The current deck is the one I posted above, reaching BB_16(36).
For a while, we thought we would be able to reach BB_17, with a neat trick to get a lot of copies of Unstable Shapeshifter, and turning them into Liege of the Hollows so that they could be sacrificed and produce a lot of Squirrels each time. Unfortunately, Unstable Shapeshifter can be turned into a copy of Sek'Kuar, Deathkeeper, so that it can die, and we can get a haste token with Xathrid Necromancer still on the battlefield. So that seems to cut off that line of research.
It would be nice to find a replacement for Sek'Kuar, since that particular creature has been causing a lot of problems. But we haven't found any suitable replacement yet.
Jfb had an interesting thought of replacing Xathrid Necromancer with Requiem Angel, which could be used by turning all relevant creature types into creature type X, except for the one creature type that we wanted. This would obviously require more Dralnu's Crusades, but so long as we can Mirrorweave them, it's a small number compared to the number of Requiem Angels we need anyway. But, we haven't found an improvement using Requiem Angel yet.
I think there are probably more layers to be found - I suspect using counters are still a fruitful area to look into.
Hmm, Requiem Angel, looks trick to make work but looks actually possible, It seems a little tricky because it can't recreate the type that just died, but that shouldn't be too difficult to work around. (we can use extra creature types for that, just need to write it out)
Hmmm... is there anything interesting to fetch with Unearth? Using black mana is good, since that tends to be the color that is hard to use - we could fetch a creature, and make a lot more with Monkey Cage, so it could work as a layer.
Kederekt Leviathan is interesting, albeit perhaps a pain to work around. The flaw with other Unearth creatures is that we can play Death Pit Offering to kill the Unearth creature, play Xathrid Necromancer plus whatever other creatures, use Mirroweave to get more Necromancers, then Unearth the creature to get haste. But with Kederekt Leviathan, it will get rid of all the other nonland permanents. That actually seems really nice, and we may not even have to worry about destroy creature effects anymore.
Oh yes, we dont' want two copies of Boggart Birth Rite. We can replace the second with Spell Burst, to put the BBR back into the graveyard.
Hmmm... that means if we cast BBR from our hand, we can retrieve it, at the cost of some colorless mana for Spell Burst. So I think we can use that to replace Mystic Speculation then.
Edit: No, we have to spend blue mana on Spell Burst, so we would still need Mystic Speculation.
Edit: Oh, but how do we get the setup working if we use Kederekt Leviathan? Bringing everything back to our hands means we have to set up the Mirrorweaves again, but that will eliminate Kederekt Leviathan. Maybe some sort of Stifle? But then we can do the same thing we do with other Unearth creatures.
Edit: So, I noticed that we had a problem: We can draw Nexus of Fate with Steady Progress, and discard it to Deepwood Elder. But, this also seems to present an opportunity; we can use drawing or fetching a card to fuel Deepwood Elder. Jar of Eyeballs allows us to fetch a card from the library to discard, after a creature dies.
Of course, we will need some help getting started, but with 12 card slots left, that shouldn't present a problem.
With all that deck space, we could get a lot for the last layer if we ended on Unstable Frontier. But, with this plan, we need have three transitions for adding +1/+1 counters, creating creatures, and giving the opponent life, which seems to occupy the three remaining colors. I suppose we could try to transition from one of those into another, but I don't see a way.
chasm skulker converts +1/+1 counters into creatures, though it does need an initial card draw.
I'm concerned about Death pit offering, I thought we said that that didn't quite work? What is forcing us to sacrifice the necromancer instead of saving it?
Seems like we can go: give them a bunch of plants, play Sek'Kuar, Deathkeeper and our other creatures, Death Pit offering to get haste, Necromancer, set up with Artificial evolution and Arcbond, attack, Mirrorweave from hand.
The idea there was that we couldn't deal a lot of damage outside of combat, so once we Mirrorweaved away our hasted token, we couldn't deal a lot of damage to the opponent.
I thought Yarok would be an issue due to its lifelink, but its deathtouch means that if it were arcbonded it would kill the haste token, so it's fine. Though we still need Roar of Challenge -> Caltrolps for this to work.
Bloodsoaked Altar sacrifices a creature which is bad; can get a haste token early.
We need Leyline of Punishment in order to enable the big attack at the end.
We're also missing a Rings of Brighthearth to multiply the abilities of Floodchaser, Angelheart Vial, and Kiora; and a Caged Sun to multiply land mana,
The problem with Orbs of Warding, is that we can donate them to the opponent, and have none on our side, so that we can take damage from the computation and heal ourselves with Angelheart Vials. I suppose in a BB computation we would run out of Vials, but we could just run a smaller computation that we can gain life with. So we want something symmetrical. A symmetrical static effect would be better of course, but I don't know of any.
Ah, Bloodsoaked Altar doesn't work. Is there some other way to pay life to create creatures? Acorn Harvest would be nice, except that Recoup gives it an extra flashback. Phyrexian Processor can put a creature into play during a computation.
Edit: So, an alternative plan to put Unstable Frontier at the end, is to have planeswalkers below artifacts, transitioning to The Chain Veil. This would be pretty simple, if we had a safe planeswalker that could generate only red mana, but all the red mana generators seem to have some problem or another. Lord Windgrace and Wrenn and Six can fetch lands from the graveyard, but they can also destroy creatures. So that seems to leave just Kiora, the Crashing Wave. How do we bounce a land that produces only red mana? The possibilities include basic lands, snow lands, legendary lands, lands that can sacrifice themselves, and lands that can turn into creatures. Can any of those be brought back to hand, using only red and colorless mana?
Edit: So, I didn't find a way to bounce a red mana land without messing up Unstable Frontier, but I found an alternative plan: Use a storage land to get a lot of red mana with each tap, giving us another layer, and just giving up on the Unstable Frontier layer. So we wind up with:
Edit: Hmmm, I thought that we would get an extra layer through Rowan Kenrith's emblems, but it looks like we don't. Each time we resolve a RW ultimate ability, we about double the number of emblems. So each new tapping of The Chain Veil will get exponentially more copies thanks to emblems, which is not enough. The emblems don't actually update to the big number until we resolve an Echo Storm, I think. So, I guess it's back to the Kiora-last version.
Edit: Oh, but Repeated Reverberation will get us those emblems, and will also get us a layer for Kiora as well, I think. So that bumps this version up 2 layers, nice.
Edit: Flaring Pain is an instant, which can turn off the damage prevention from Kiora's +1, which can halt a computation. Leyline of Punishment should work though.
Edit: Argh - Floodchaser has a problem, we can remove all the counters and let it die, creating a hasted token.
That really hurts, straight up losing two layers. I do notice that we need blue mana to remove the counters though, so we need a blue mana to get started. Perhaps we could make it so that we needed combat in order to get the blue mana? But, if we could get blue mana every combat, that would be too cheap. So it would have to be something that required combat, and could only be done once. I have no idea what that would be.
Hmm, that maybe works - and since we already have Dowsing Dagger and no Unstable Frontier, we don't even need to make any changes!
Edit: So the next issue is, how do we go about getting started, if we don't have early access to blue mana? The original plan was to create some Plant tokens on the opponent's side, Mirrorweave them to Dralnu's Crusade tokens, then put a bunch more Plant tokens on the opponent's side and Mirrorweave them to Xathrid Necromancers. So we would have to put Dowsing Dagger into play a whole bunch of times. (something like 2^2^1000?) How would we do that without any blue mana? Perhaps we could use some other color of mana? Mirrorworks could help, we could then bounce or flicker artifacts instead of copying them.
It would be nice if we could get an initial combat before we finished making Necromancers, but with the current setup, we can't Mirrorweave anymore once we make the hasted token.
How about Argivian Find + By Force + Mirrorworks? That way we can copy enchantments just from red, allowing for Rings of Brighthearth and The Chain Veil to actually be worth layers. Though artifact recursion is incompatible with general land destruction (because of the dowsing dagger), and we'd also need to find a new use for blue.
Hmmm, I'm not sure how that works. That would put artifacts below red, and planeswalkers below artifacts - but we're using red mana to cast Seize the Day. Is there a suitable replacement for Seize the Day?
And we need a way to reset our enchantments like TYS after they briefly become Dralnu's Crusades.
As the one free cast of Echo Storm needs to be after we have a lot of storm, we can't have two amulet of vigor to make red mana with the storage land.
Mirrorworks looks helpful to fix that problem, with something like Steel Sabotage to enable bouncing. Though that can bounce a donated caged sun to induce a halt.
Hmm, most things that bounce artifacts are instants, or like Baral's Expertise also bounce creatures.
Edit: also we would need to not use Black Lotus for the start with any general artifact recursion.
Unfortunately, general creature bounce means that we can bounce Xathrid Necromancer after we have Mirrorweaved the opponent their own necromancers. Then, we can use Death Pit Offering to kill some other creature (like Deepwood Elder), get a hasted token, and replay Xathrid Necromancer.
Edit: Hmmm wait... is that actually a problem anymore? The idea behind the infinite was that Xathrid Necromancer was would keep producing a token, until we didn't want it to anymore, and put the token creation under an Arcbond trigger. But, since our Xathrid Necromancer is of the same type as the token creature that creates a creature upon dying, it will die as well. So we can't string this out for an arbitrarily long time, I think.
I think it works the same no matter how many many Necromancers we have? Each Necromancer can be set to produce a creature upon a creature dying, but the Necromancer will die as well. So, we get a finite number of choices to affect the computation. With a finite number of choices, it is impossible to string the computation arbitrarily long and then halt it.
So I'm starting to think that it's okay to have Necromancers. Does this make sense?
Edit: No, we have that spare creature type that we can use to keep the Necromancers alive. What about Rotlung Reanimators? Then, if we set X to produce X, then Rotlung Reanimator will just have creature X, and will die then. So at least, one Reanimator isn't enough to go infinite. What about two Rotlung Reanimators? We can have X set to produce Y, and Y set to produce X in that case. Hmm, I'm not sure about this. What do you guys think?
Hmm, interesting. One RR set to "when X dies make X" seems safe, but one set to "when X dies make Y" could be kept alive by other Y so might not be. If it were safe to just have any number of RRs then Sek'kuar wouldn't even be needed which would be nice. But I'm not certain that it is safe, and I believe it most likely isn't.
Another issue with RR would be that it makes a lot of creatures on our own side which could mess with creature layers.
Edit: Having just one RR, set to "when X dies make Y", while the opponent also has a system of RRs, is bad. When an X dies, your RR can be kept alive by Ys, and you essentially choose whether a Y gets created (and seen by the computation) or not. That X death can also trigger a computation on the opponents side, which will convert the Ys into twice as many Xs (thus keeping our RR alive still), and also checks whether the number of Ys was even or odd. If it's odd, halt, otherwise convert the Xs into twice as many Ys and repeat. So your choice of whether the Y got seen determines whether it halts.
Where are we at now?
For a while, we thought we would be able to reach BB_17, with a neat trick to get a lot of copies of Unstable Shapeshifter, and turning them into Liege of the Hollows so that they could be sacrificed and produce a lot of Squirrels each time. Unfortunately, Unstable Shapeshifter can be turned into a copy of Sek'Kuar, Deathkeeper, so that it can die, and we can get a haste token with Xathrid Necromancer still on the battlefield. So that seems to cut off that line of research.
It would be nice to find a replacement for Sek'Kuar, since that particular creature has been causing a lot of problems. But we haven't found any suitable replacement yet.
Jfb had an interesting thought of replacing Xathrid Necromancer with Requiem Angel, which could be used by turning all relevant creature types into creature type X, except for the one creature type that we wanted. This would obviously require more Dralnu's Crusades, but so long as we can Mirrorweave them, it's a small number compared to the number of Requiem Angels we need anyway. But, we haven't found an improvement using Requiem Angel yet.
I think there are probably more layers to be found - I suspect using counters are still a fruitful area to look into.
Being a bigger creature make the angel harder to reanimate, so something like unearth or gruesome menagerie can be used instead of the Claim // Fame that was causing troubles. (Call to the netherworld is also an option but gets sek'kaur too)
As for replacing Sek'Kuar, Deathkeeper, there's not really anything with quite the same effect. Altac Bloodseeker? With the unearth plan, Kederekt Leviathan?
Also expanding on the neat boggart birth rite tech, March from the Tomb does the same thing but for allies. (unfortunately the other similar cards don't work: Misery charm and cruel revival kill things and Grim Captain's Call doesn't target)
Edit: Oh, and we only want one copy of Boggart Birth rite, as it can fetch the other copy for infinite storm.
Kederekt Leviathan is interesting, albeit perhaps a pain to work around. The flaw with other Unearth creatures is that we can play Death Pit Offering to kill the Unearth creature, play Xathrid Necromancer plus whatever other creatures, use Mirroweave to get more Necromancers, then Unearth the creature to get haste. But with Kederekt Leviathan, it will get rid of all the other nonland permanents. That actually seems really nice, and we may not even have to worry about destroy creature effects anymore.
March for the Tomb - I looked into it for fetching Jwari Shapeshifter, but that can copy Xathrid Necromancer.
Oh yes, we dont' want two copies of Boggart Birth Rite. We can replace the second with Spell Burst, to put the BBR back into the graveyard.
Hmmm... that means if we cast BBR from our hand, we can retrieve it, at the cost of some colorless mana for Spell Burst. So I think we can use that to replace Mystic Speculation then.
Edit: No, we have to spend blue mana on Spell Burst, so we would still need Mystic Speculation.
Edit: Oh, but how do we get the setup working if we use Kederekt Leviathan? Bringing everything back to our hands means we have to set up the Mirrorweaves again, but that will eliminate Kederekt Leviathan. Maybe some sort of Stifle? But then we can do the same thing we do with other Unearth creatures.
- Crucible of the Spirit Dragon can get creature/tribal-only mana (can be hacked to any creature type)
- Floodchaser can make a lot of lands into islands for one counter via Rings of brighthearth
Remove Steady Progress, so that we lose a layer from Red Mana Battery. Then, we have Floodchaser turn a bunch of Great Furnaces into Islands at the cast of 1 counter, and we can have Elven Rite add a bunch of +1/+1 counters to Floodchaser at the cost of a green mana. So that's two layers better than Splendid Reclamation.
Edit: So, I noticed that we had a problem: We can draw Nexus of Fate with Steady Progress, and discard it to Deepwood Elder. But, this also seems to present an opportunity; we can use drawing or fetching a card to fuel Deepwood Elder. Jar of Eyeballs allows us to fetch a card from the library to discard, after a creature dies.
So, what about:
2 Eureka
3 Omniscience
4 Thousand-Year Storm
5 Spellweaver Volute
6 Pull from Eternity
7 Recoup
8 Coat of Arms
9 Xathrid Necromancer
10 Arcbond
11 Artificial Evolution
12 Mirrorweave
13 Dowsing Dagger
14 Dralnu's Crusade
15 Starfield of Nyx
17 Forebear's Blade
18 Chameleon Blur
19 Upwelling
20 Orb of Dreams
21 Death Pit Offering
22 Sek'Kuar, Deathkeeper
23 Mystic Speculation
24 Mana Echoes
25 Seize the Day
26 Great Furnace
27 Amulet of Vigor
28 Echo Storm
29 Svyelunite Temple
30 Floodchaser
32 Deepwood Elder
33 Thousand-Year Elixir
34 Jar of Eyeballs
35 Nexus of Fate
36 Moan of the Unhallowed
37 Nurturing Peatland
38 Splendid Reclamation
39 Angelheart Vial
40 Flame Rift
41 Healing Hands
42 Unstable Frontier
43 Soratami Mirror Guard
4 Kiora, the Crashing Wave
1 Oath of Teferi
Of course, we will need some help getting started, but with 12 card slots left, that shouldn't present a problem.
With all that deck space, we could get a lot for the last layer if we ended on Unstable Frontier. But, with this plan, we need have three transitions for adding +1/+1 counters, creating creatures, and giving the opponent life, which seems to occupy the three remaining colors. I suppose we could try to transition from one of those into another, but I don't see a way.
I'm concerned about Death pit offering, I thought we said that that didn't quite work? What is forcing us to sacrifice the necromancer instead of saving it?
Seems like we can go: give them a bunch of plants, play Sek'Kuar, Deathkeeper and our other creatures, Death Pit offering to get haste, Necromancer, set up with Artificial evolution and Arcbond, attack, Mirrorweave from hand.
2 Eureka
3 Omniscience
4 Thousand-Year Storm
5 Spellweaver Volute
6 Pull from Eternity
7 Recoup
8 Coat of Arms
9 Xathrid Necromancer
10 Arcbond
11 Artificial Evolution
12 Mirrorweave
13 Dowsing Dagger
14 Dralnu's Crusade
15 Starfield of Nyx
16 Roar of Challenge
17 Forebear's Blade
18 Chameleon Blur
19 Upwelling
20 Orb of Dreams
22 Sek'Kuar, Deathkeeper
23 Mystic Speculation
24 Mana Echoes
25 Seize the Day
26 Great Furnace
27 Amulet of Vigor
28 Echo Storm
29 Floodchaser
30 Courage in Crisis
31 Deepwood Elder
32 Thousand-Year Elixir
33 Jar of Eyeballs
34 Nexus of Fate
35 Bloodsoaked Altar
36 Angelheart Vial
37 Flame Rift
39 Azorius Chancery
40 Kiora, the Crashing Wave
41 Syndicate Guildmage
42 Warden of the Eye
43 Settle Beyond Reality
1 Unstable Frontier
4 Vesuva
4 Yarok, the Desecrated
4 Darigaaz's Caldera
4 Dromar's Cavern
Warden of the Eye doesn't work since it can get back Artificial Evolution for use during a computation.
I thought Yarok would be an issue due to its lifelink, but its deathtouch means that if it were arcbonded it would kill the haste token, so it's fine. Though we still need Roar of Challenge -> Caltrolps for this to work.
Bloodsoaked Altar sacrifices a creature which is bad; can get a haste token early.
We need Leyline of Punishment in order to enable the big attack at the end.
We're also missing a Rings of Brighthearth to multiply the abilities of Floodchaser, Angelheart Vial, and Kiora; and a Caged Sun to multiply land mana,
Ah, Bloodsoaked Altar doesn't work. Is there some other way to pay life to create creatures? Acorn Harvest would be nice, except that Recoup gives it an extra flashback. Phyrexian Processor can put a creature into play during a computation.
Edit: So, an alternative plan to put Unstable Frontier at the end, is to have planeswalkers below artifacts, transitioning to The Chain Veil. This would be pretty simple, if we had a safe planeswalker that could generate only red mana, but all the red mana generators seem to have some problem or another. Lord Windgrace and Wrenn and Six can fetch lands from the graveyard, but they can also destroy creatures. So that seems to leave just Kiora, the Crashing Wave. How do we bounce a land that produces only red mana? The possibilities include basic lands, snow lands, legendary lands, lands that can sacrifice themselves, and lands that can turn into creatures. Can any of those be brought back to hand, using only red and colorless mana?
Edit: So, I didn't find a way to bounce a red mana land without messing up Unstable Frontier, but I found an alternative plan: Use a storage land to get a lot of red mana with each tap, giving us another layer, and just giving up on the Unstable Frontier layer. So we wind up with:
2 Eureka
3 Omniscience
4 Thousand-Year Storm
5 Spellweaver Volute
6 Pull from Eternity
7 Recoup
8 Coat of Arms
9 Xathrid Necromancer
10 Arcbond
11 Artificial Evolution
12 Mirrorweave
13 Dowsing Dagger
14 Dralnu's Crusade
15 Starfield of Nyx
17 Forebear's Blade
18 Chameleon Blur
19 Upwelling
21 Death Pit Offering
22 Sek'Kuar, Deathkeeper
23 Mystic Speculation
24 Fuel for the Cause
25 Mana Echoes
26 Seize the Day
27 Mercadian Bazaar
28 Amulet of Vigor
29 Dwarven Miner
30 Petrified Field
31 Kiora, the Crashing Wave
32 Rowan Kenrith
34 Echo Storm
35 Floodchaser
36 Caged Sun
37 Blessings of Nature
38 Deepwood Elder
39 Thousand-Year Elixir
40 Jar of Eyeballs
41 Nexus of Fate
42 Moan of the Unhallowed
43 Nurturing Peatland
44 Angelheart Vial
45 Flame Rift
46 Healing Hands
47 Flaring Pain
Edit: With a little readjustment, we can put opponent life gain at the end:
2 Eureka
3 Omniscience
4 Thousand-Year Storm
5 Spellweaver Volute
6 Pull from Eternity
7 Recoup
8 Coat of Arms
9 Xathrid Necromancer
10 Arcbond
11 Artificial Evolution
12 Mirrorweave
13 Dowsing Dagger
14 Dralnu's Crusade
15 Starfield of Nyx
16 Caltrops
17 Forebear's Blade
18 Chameleon Blur
19 Upwelling
22 Sek'Kuar, Deathkeeper
23 Mystic Speculation
24 Fuel for the Cause
25 Mana Echoes
26 Seize the Day
27 Mercadian Bazaar
28 Amulet of Vigor
29 Dwarven Miner
30 Petrified Field
31 Kiora, the Crashing Wave
32 Rowan Kenrith
33 The Chain Veil
34 Echo Storm
35 Floodchaser
36 Caged Sun
37 Blessings of Nature
38 Deepwood Elder
39 Thousand-Year Elixir
41 Nexus of Fate
42 Icatian Town
43 Plains
44 Sinkhole
45 Nurturing Peatland
46 Angelheart Vial
47 Flame Rift
48 Oona's Grace
49 Spiritual Focus
50 Coercion
51 Alhammarret's Archive
52 Mirror Gallery
53 Harmless Offering
54 Possessed Portal
55 Flaring Pain
4 Centaur Peacemaker
1 Skystreamer
Edit: Hmmm, I thought that we would get an extra layer through Rowan Kenrith's emblems, but it looks like we don't. Each time we resolve a RW ultimate ability, we about double the number of emblems. So each new tapping of The Chain Veil will get exponentially more copies thanks to emblems, which is not enough. The emblems don't actually update to the big number until we resolve an Echo Storm, I think. So, I guess it's back to the Kiora-last version.
Edit: Oh, but Repeated Reverberation will get us those emblems, and will also get us a layer for Kiora as well, I think. So that bumps this version up 2 layers, nice.
Still it would be nice if the Flaring pain spot was also useful for the rest of the combo.
Edit: Flaring Pain is an instant, which can turn off the damage prevention from Kiora's +1, which can halt a computation. Leyline of Punishment should work though.
Edit: Argh - Floodchaser has a problem, we can remove all the counters and let it die, creating a hasted token.
That really hurts, straight up losing two layers. I do notice that we need blue mana to remove the counters though, so we need a blue mana to get started. Perhaps we could make it so that we needed combat in order to get the blue mana? But, if we could get blue mana every combat, that would be too cheap. So it would have to be something that required combat, and could only be done once. I have no idea what that would be.
Edit: So the next issue is, how do we go about getting started, if we don't have early access to blue mana? The original plan was to create some Plant tokens on the opponent's side, Mirrorweave them to Dralnu's Crusade tokens, then put a bunch more Plant tokens on the opponent's side and Mirrorweave them to Xathrid Necromancers. So we would have to put Dowsing Dagger into play a whole bunch of times. (something like 2^2^1000?) How would we do that without any blue mana? Perhaps we could use some other color of mana? Mirrorworks could help, we could then bounce or flicker artifacts instead of copying them.
It would be nice if we could get an initial combat before we finished making Necromancers, but with the current setup, we can't Mirrorweave anymore once we make the hasted token.
And we need a way to reset our enchantments like TYS after they briefly become Dralnu's Crusades.
As the one free cast of Echo Storm needs to be after we have a lot of storm, we can't have two amulet of vigor to make red mana with the storage land.
Mirrorworks looks helpful to fix that problem, with something like Steel Sabotage to enable bouncing. Though that can bounce a donated caged sun to induce a halt.
Hmm, most things that bounce artifacts are instants, or like Baral's Expertise also bounce creatures.
Edit: also we would need to not use Black Lotus for the start with any general artifact recursion.
I guess we could have a second Amulet of Vigor, or a Sculpting Steel, if we need one. But, it looks like we are running dangerously low on slots.
Black Lotus can also be replaced - for another two card slots. Yikes!
Then Mirrorworks can help us get stated and let us cut echo storm?
We obviously need to cut the ETB gain life guys, but they were at the very end anyway.
Edit: Hmmm wait... is that actually a problem anymore? The idea behind the infinite was that Xathrid Necromancer was would keep producing a token, until we didn't want it to anymore, and put the token creation under an Arcbond trigger. But, since our Xathrid Necromancer is of the same type as the token creature that creates a creature upon dying, it will die as well. So we can't string this out for an arbitrarily long time, I think.
I think it works the same no matter how many many Necromancers we have? Each Necromancer can be set to produce a creature upon a creature dying, but the Necromancer will die as well. So, we get a finite number of choices to affect the computation. With a finite number of choices, it is impossible to string the computation arbitrarily long and then halt it.
So I'm starting to think that it's okay to have Necromancers. Does this make sense?
Edit: No, we have that spare creature type that we can use to keep the Necromancers alive. What about Rotlung Reanimators? Then, if we set X to produce X, then Rotlung Reanimator will just have creature X, and will die then. So at least, one Reanimator isn't enough to go infinite. What about two Rotlung Reanimators? We can have X set to produce Y, and Y set to produce X in that case. Hmm, I'm not sure about this. What do you guys think?
Another issue with RR would be that it makes a lot of creatures on our own side which could mess with creature layers.
Edit: Having just one RR, set to "when X dies make Y", while the opponent also has a system of RRs, is bad. When an X dies, your RR can be kept alive by Ys, and you essentially choose whether a Y gets created (and seen by the computation) or not. That X death can also trigger a computation on the opponents side, which will convert the Ys into twice as many Xs (thus keeping our RR alive still), and also checks whether the number of Ys was even or odd. If it's odd, halt, otherwise convert the Xs into twice as many Ys and repeat. So your choice of whether the Y got seen determines whether it halts.