Seeing as you have 8 sources of b mana why not consider a misers copy of vault of the archangel, the lifelink deathtouch can prove to be useful. I have a w/b/r tokens list and it proves solid.
Burn at the Stake is a stellar card in a tokens deck, especially when they have vigilence.
There are only two cards I can think of that combo infinitely with this. Maybe three in all of magic. That hardly falls into the category of "Way to abusable". Cards that have infinite combos get printed all the time, and most people would agree that's not necessarily a bad thing, it allows for a whole archetype. If a card that makes a two card combo with two, maybe three other things, is fundamentally broken then there is certainly a serious problem.
*eyeroll*
Off the top of my head: if you can reanimate repeatedly and then sac a creature for less mana than you can tap for you have infinite mana.
There are plenty of repeatable sac outlets.
Reanimation is slightly more difficult, but not too hard to find. 1 example being Golgari guildmage, it goes infinite when you have 7 mana plus a 1 drop in play and one in the yard.
Havengul Lich also has similar issues, but you need 2 more mana than the creature you plan to cast and a different sac outlet.
Hadday, the Ancient Fountain
Legendary Land (R)
Hadday, the Ancient Fountain enters the battlefield tapped. T: Add one mana of any color to your mana pool.
Discard a card: Untap Hadday.
IIW: a spell or mechanic that fuses two creatures into one
Seems pretty balanced, would almost be a auto include in any 3 colour or greater EDH deck. Also possibly constructed playable. Really good in limited. 7/10
Node Molder(G/U)(G/U)
Creature - Elf Wizard {R}
Basic lands you control have "T:Untap target nonbasic land."
2/2
IIW: How much interaction can you cram into six words of rules text?
I really like the interaction with Maze of Ith/Thawing Glaciers. Certainly good in constructed where any duals are present, even better with karoos. 7.5/10
Conservation Theory3G
Enchantment (R)
Sacrifice a land: Untap all lands you control. As the Flamekins waged war against the Great Forest, the elves
did their best to carry the mana to untouched groves.
Iiwsig
This is really good, and if you play this with any way of returning lands is even better. With knight of the reliquary is a little bonkers. 7/10
Kheero Bazaar
Land {R} T:Add 1 to your mana pool. ,T:Untap Kheero Bazaar and target land you don't control, then exchange control of them.
As a Zerduu player, this is awesome and oh so funny. With any land that produces more than 2 mana this plus a willing partner generates infinite mana for both parties. 8/10
Catalyzing Fields [R]
Legendary Land
Catalyzing Fields doesn't untap during your untap step.
:symtap:: Until end of turn, spells you cast cost 1 less to cast. Landfall -- Whenever a land enters the battlefield under your control, untap Catalzying Fields.
IIW: Emotion-inspiring flavortext
With the not untapping without landfall, this makes your land drops so much better, esp with something like a fireball in hand. Makes silly things happen in egg decks. Possible to go off turn 3??
6/10
Weatherheim, the Last Bastion
Legendary Land (R) T: Add W to your mana pool
Whenever a land you control is put into the graveyard from the battlefield, untap Weatherheim, the Last Bastion.
"With every day, more and more of our homes are destroyed by the Scethian war machines, but here we will hold firm, here, we will stand against the demon's influence."
-- Cade, Refugee Leader
IIW: Make an artifact from an historic civilization.
This is really nice with fetchlands/stripmine and co, otherwise not too great as you are not going to reliably be able to get lands in the bin .
6.5/10
Whenever a land an opponent controls becomes tapped, you may untap target land you control.
"The leaves may rust and fall. But soon they will return, just as the sun does every morning. Bright and and bursting with life."
IIW: Blow something up.
Oh the shenanigans, in a u/g control deck this is cruel, and probably what it would be used in.
7/10
Brushbraid Elf2RG
Creature - Elf Shaman (U)
Haste, Crickety (When you cast Brushbraid Elf, you may untap a number of lands equal to one less than its converted mana cost.)
3/2
IIW: Tricky punches
Nice take on the free spells mechanic, however it probably should be a etb effect rather than on casting.
6/10
Fertile Blessing1G
Instant C
Counter target spell that targets a land or creature you control
and untap target non-basic land.
IIW: Narrow but 0
This feels like the kind of counterspell green would do, but the untapping feels tacked on and not quite right, perhaps if it was on basics it might be better...
6/10
Gravetilling2GG Enchantment (R)
Whenever a nontoken creature you control dies, untap all lands you control. "Life and death are not as disparate as you believe. In death, we make way for new life. We live on through the blossoms as we did through our bodies."
IIW: Demons and deals
This is probably undercosted, I think it probably should be 3GG. Given any sac outlet and something like gravecrawler, it is way too abuseable.
6.5/10
That which Consumes7
Creature - Eldrazi (R)
Annihilator 1
Whenever an opponent sacrifices a permanent, put a token copy of ~ into play under your control.
5/5
Figment of MemoryUU
Creature - Illusion (R)
At the beginning of your upkeep add an aether counter to ~.
When ~ has 3 or more aether counters on it you may sacrifice it, if you do, reveal cards from the top of your library until you reveal a creature card, put that card on the battlefield, then put all other cards on the bottom of your library in any order.
1/1
Electrolysis Engine4
Artifact (R) UR,T, Sacrifice a nonland pemanent: Electrolysis Engine deals damage to target creature or player equal to the sacrificed permanent's converted mana cost. "And then he asked me 'Izzet safe?'"
IIW Sig
You should win just for that flavor text!
Draughts of wisdom 3U
Instant (U)
Tap up to 5 target creatures. For each creature tapped this way it's controller draws a card.
Champion of ZendikarWUBRG
Legendary Creature - Human Warrior Ally (M)
Whenever ~ or another Ally enters the battlefield under your control, you may search your library for an Ally card with converted mana cost is less than or equal to the number of Allies you control, reveal that card, and put it into your hand. Then shuffle your library. All gather beneath his banner
4/4
Burn at the Stake is a stellar card in a tokens deck, especially when they have vigilence.
Instant - C
Target creature gains flying until end of turn.
/////
DownG
Instant - C
Target creature loses flying until end of turn.
IIW: Dwarves
Off the top of my head: if you can reanimate repeatedly and then sac a creature for less mana than you can tap for you have infinite mana.
There are plenty of repeatable sac outlets.
Reanimation is slightly more difficult, but not too hard to find. 1 example being Golgari guildmage, it goes infinite when you have 7 mana plus a 1 drop in play and one in the yard.
Havengul Lich also has similar issues, but you need 2 more mana than the creature you plan to cast and a different sac outlet.
Seems pretty balanced, would almost be a auto include in any 3 colour or greater EDH deck. Also possibly constructed playable. Really good in limited. 7/10
I really like the interaction with Maze of Ith/Thawing Glaciers. Certainly good in constructed where any duals are present, even better with karoos. 7.5/10
This is really good, and if you play this with any way of returning lands is even better. With knight of the reliquary is a little bonkers. 7/10
As a Zerduu player, this is awesome and oh so funny. With any land that produces more than 2 mana this plus a willing partner generates infinite mana for both parties. 8/10
Can wizards print this already??? I love this mechanic. 9.5/10
With the not untapping without landfall, this makes your land drops so much better, esp with something like a fireball in hand. Makes silly things happen in egg decks. Possible to go off turn 3??
6/10
This is really nice with fetchlands/stripmine and co, otherwise not too great as you are not going to reliably be able to get lands in the bin .
6.5/10
This is very nice, ok in limited, fun in edh, boderline constructed playable, but probably in a combo deck.
7/10
CCCCCombo. Silly with so many things. Probably ban worthy in some of the larger formats, given it can make inf mana turn 2...
5/10
Go go manlands! Given that this can basically be a free spell, it is pretty good.
Possibly could have been an instant.
7/10
Oh the shenanigans, in a u/g control deck this is cruel, and probably what it would be used in.
7/10
Nice take on the free spells mechanic, however it probably should be a etb effect rather than on casting.
6/10
This feels like the kind of counterspell green would do, but the untapping feels tacked on and not quite right, perhaps if it was on basics it might be better...
6/10
I can see this actually being printed sometime in the future
9/10
This is mean, casting this during someones upkeep is cruel. In limited it would be a very early pick for control. I like it....
8.5/10
This is probably undercosted, I think it probably should be 3GG. Given any sac outlet and something like gravecrawler, it is way too abuseable.
6.5/10
Another 'free' spell, this feels ok in terms of the free spells. Would be printable.
8/10
And the winner is
Judging now!
Creature - Demon
Flying, Trample
~ Gets -1/-1 for each creature your opponents control.
8/8
IIW: untaping lands
Creature - Eldrazi (R)
Annihilator 1
Whenever an opponent sacrifices a permanent, put a token copy of ~ into play under your control.
5/5
IIW: cats
Worlds End WWWUUUBBBRRRGGG
Sorcery (R)
Target player loses the game.
IIW: cmc 0
Sorcery (R)
~ deals damage to each opponent equal to twice the number of permanents they control that they do not own.
IIW: a much larger dave
Creature - Illusion (R)
At the beginning of your upkeep add an aether counter to ~.
When ~ has 3 or more aether counters on it you may sacrifice it, if you do, reveal cards from the top of your library until you reveal a creature card, put that card on the battlefield, then put all other cards on the bottom of your library in any order.
1/1
IIW: Three words of rules text
Sorcery (U)
Target player discards a card at random.
IIW: Three words of rules text
You should win just for that flavor text!
Draughts of wisdom 3U
Instant (U)
Tap up to 5 target creatures. For each creature tapped this way it's controller draws a card.
IIW: Aggro mana dork
Legendary Creature - Human Warrior Ally (M)
Whenever ~ or another Ally enters the battlefield under your control, you may search your library for an Ally card with converted mana cost is less than or equal to the number of Allies you control, reveal that card, and put it into your hand. Then shuffle your library.
All gather beneath his banner
4/4
IIW: Goats, Stoats and Moats
Artifact - Equipment U
Equipped creature has haste and flying
Equip 2
IIW: Dune
Sorcery U
Flip a coin, if you win the flip, target creature you control deals damage equal to it's power to target creature. Repeat.
IIW: Goats