My favorite part of mutate as an ability is that it allows players to meld together new cards with old ones, creating a number of wild options. Brewing for Otrimi, the Ever-Playful, I wanted to see what compelling options there were for mutation bases existed. Even though mutate cards were built to negate their own card disadvantage and Otrimi was designed to help you rebuild a mutate chain, it's still worth asking what cards you should build off of.
Cards you might play either way Baleful Strix: Allows Otrimi to mutate on curve, grants additional evasion and deathtouch (which works really well with Otrimi's trample), and it replaces itself. Putting Otrimi on top also blocks artifact destruction. Coiling Oracle: Allows Otrimi to mutate on curve and it replaces itself. Wood Elves: Replaces itself and makes sure that Otrimi comes down on curve. Edric, Spymaster of Trest: A generally useful card that should replace itself if you mutate the turn you attack with your Otrimi chain. Phyrexian Metamorph: It fits perfectly into the curve if you pay the phyrexian mana cost and allows you to slam the abilities of the best (nonhuman) creature on the board onto Otrimi. Gilded Drake: As Phyrexian Metamorph.
Protect the Chain Predator Ooze: While this card does not allow for an on-curve Otrimi, making the chain indestructible is really good and granting trample and commander damage potential onto an ever-growing body seems like good sense to me. Rhonas the Indomitable / Kefnet the Mindful / Bontu the Glorified: While these are Terrible options for Otrimi itself, these are cheap indestructible creatures if you just want to make a mutate value-chain. Elusive Tormentor: While this isn't "on curve", the ability to get a hexproof, indestructible, unblockable 6/6 mist is very tempting. Slippery Bogle / Gladecover Scout : cheap hexproof bases. Darksteel Myr: on-curve indestructibility. Yahenni, Undying Partisan: While keeping Yahenni alive requires playing creatures outside of the mutate-chain, it still has resilience with a growing body and adds haste in the late-game. Silhana Ledgewalker: Evasion to Aid Otrimi + Hexproof for protection. Both fall perfectly on curve. Thrun, the Last Troll / Troll Ascetic: Hexproof and Regeneration are a potent Mix. Kathari Remnant: A flying, regenerating target that replaces itself. Lotleth Troll: On-curve regeneration and lets you get mileage out of Otrimi's triggered ability even after you have brought back the team (discard a mutator to add a +1/+1 counter and then bring it back). Mire Boa: If you're running Urborg, this card can make the chain unblockable and grant cheap protection. Mischievous Poltergeist: One of the few "free" sources of regeneration. Also adds evasion. Mossbridge Troll: While this card is a late-game actor, I really like it. The first ability makes it a real pain to deal with and the secondary ability works really well when this guy has trample... and deals commander damage... Nightscape Familiar: To my understanding, this allows for a Turn 3 Otrimi who can regenerate and who continued to provide blue spells with a passive discount (a bit better value than turning a mana dork into Otrimi, in my opinion). Will-o'-the-Wisp: One mana to add flying and regeneration to your chain is a pretty good deal. The fact that you can throw down the wisp, mutate it, and still have a mana open to regenerate for 6 mana (Otrimi's "normal" CMC) is worth noting. Sapling of Colfenor: It's a bit expensive but it's an indestructible base that grabs card advantage.
Power Matters Cold-Eyed Selkie: Nice card draw. Cephalid Constable: brutal lockdown. Needle Specter: nail down your opponent's hand Viridian Joiner: While it isn't the greatest option, the thought of evolving Otrimi onto this on turn 4 before tapping it for 6 mana (to, say, mutate Auspicious Starrix onto this and grab two more permanents) is nice.
+1/+1 Counters and Aggro Lifeblood Hydra: While this card can't be played "on curve" with Otrimi, the ability to increase the hydra's power (and the amount of lifegain and card draw) by +6 is excellent. Endless One While it isn't the most "Effective" strategy, attacking with a 9/9 trampling commander on turn 4 is always a nice feeling (note that the superior stonecoil serpent doesn't work as the protection actually blocks Otrimi's mutate ability) Hungering Hydra: The way this hydra works synergizes incredibly well with Otrimi's Trample, quickly making your commander difficult to fight if nobody draws an answer. Managorger Hydra: It makes your commander huge in short order. Not competitive but kind of fun. Mist-Syndicate Naga: Most people don't realize that added abilities from mutate are copiable traits. If you put otrimi on this on turn 4 and make a copy, the copy will also have all benefits of mutation.
Infect creatures and Cephalid Constable/Needle Specter type cards. Despite of Otrimi's ability, I think it's better for the deck to use less mutate creatures.
Infect creatures and Cephalid Constable/Needle Specter type cards. Despite of Otrimi's ability, I think it's better for the deck to use less mutate creatures.
While I can certainly understand the power of Mutate in infect colors, I can't help but think that ignoring evolve is the wrong way to ignore Otrimi. If you just want to use it as a reusable buff, you are using Otrimi as a worse Brokkos 99% of the time (paying 1 more for the initial cast is certainly worth never paying commander tax in my book). The only thing making Otrimi worth using over Brokkos is its interaction with mutate so ignoring that seems kind of silly.
With that said, it's totally possible that Brokkos is simply a better commander.
Elusive Tormentor you can discard a mutate creature for the transform cost. Transform into Insidious Mist which gives you an unblockable, hexproof, indestructible body for mutate.
Also just realized that mist-syndicate naga is pretty excellent as traits/abilities gained through mutate are copiable traits... though it might not make sense to put Otrimi in front of the chain here due to legend rule problems.
Edit: List in OP edited with suggestions from thread.
Cards you might play either way
Baleful Strix: Allows Otrimi to mutate on curve, grants additional evasion and deathtouch (which works really well with Otrimi's trample), and it replaces itself. Putting Otrimi on top also blocks artifact destruction.
Coiling Oracle: Allows Otrimi to mutate on curve and it replaces itself.
Wood Elves: Replaces itself and makes sure that Otrimi comes down on curve.
Edric, Spymaster of Trest: A generally useful card that should replace itself if you mutate the turn you attack with your Otrimi chain.
Phyrexian Metamorph: It fits perfectly into the curve if you pay the phyrexian mana cost and allows you to slam the abilities of the best (nonhuman) creature on the board onto Otrimi.
Gilded Drake: As Phyrexian Metamorph.
Protect the Chain
Predator Ooze: While this card does not allow for an on-curve Otrimi, making the chain indestructible is really good and granting trample and commander damage potential onto an ever-growing body seems like good sense to me.
Rhonas the Indomitable / Kefnet the Mindful / Bontu the Glorified: While these are Terrible options for Otrimi itself, these are cheap indestructible creatures if you just want to make a mutate value-chain.
Elusive Tormentor: While this isn't "on curve", the ability to get a hexproof, indestructible, unblockable 6/6 mist is very tempting.
Slippery Bogle / Gladecover Scout : cheap hexproof bases.
Darksteel Myr: on-curve indestructibility.
Yahenni, Undying Partisan: While keeping Yahenni alive requires playing creatures outside of the mutate-chain, it still has resilience with a growing body and adds haste in the late-game.
Silhana Ledgewalker: Evasion to Aid Otrimi + Hexproof for protection. Both fall perfectly on curve.
Thrun, the Last Troll / Troll Ascetic: Hexproof and Regeneration are a potent Mix.
Kathari Remnant: A flying, regenerating target that replaces itself.
Lotleth Troll: On-curve regeneration and lets you get mileage out of Otrimi's triggered ability even after you have brought back the team (discard a mutator to add a +1/+1 counter and then bring it back).
Mire Boa: If you're running Urborg, this card can make the chain unblockable and grant cheap protection.
Mischievous Poltergeist: One of the few "free" sources of regeneration. Also adds evasion.
Mossbridge Troll: While this card is a late-game actor, I really like it. The first ability makes it a real pain to deal with and the secondary ability works really well when this guy has trample... and deals commander damage...
Nightscape Familiar: To my understanding, this allows for a Turn 3 Otrimi who can regenerate and who continued to provide blue spells with a passive discount (a bit better value than turning a mana dork into Otrimi, in my opinion).
Will-o'-the-Wisp: One mana to add flying and regeneration to your chain is a pretty good deal. The fact that you can throw down the wisp, mutate it, and still have a mana open to regenerate for 6 mana (Otrimi's "normal" CMC) is worth noting.
Sapling of Colfenor: It's a bit expensive but it's an indestructible base that grabs card advantage.
Power Matters
Cold-Eyed Selkie: Nice card draw.
Cephalid Constable: brutal lockdown.
Needle Specter: nail down your opponent's hand
Viridian Joiner: While it isn't the greatest option, the thought of evolving Otrimi onto this on turn 4 before tapping it for 6 mana (to, say, mutate Auspicious Starrix onto this and grab two more permanents) is nice.
+1/+1 Counters and Aggro
Lifeblood Hydra: While this card can't be played "on curve" with Otrimi, the ability to increase the hydra's power (and the amount of lifegain and card draw) by +6 is excellent.
Endless One While it isn't the most "Effective" strategy, attacking with a 9/9 trampling commander on turn 4 is always a nice feeling (note that the superior stonecoil serpent doesn't work as the protection actually blocks Otrimi's mutate ability)
Hungering Hydra: The way this hydra works synergizes incredibly well with Otrimi's Trample, quickly making your commander difficult to fight if nobody draws an answer.
Managorger Hydra: It makes your commander huge in short order. Not competitive but kind of fun.
Mist-Syndicate Naga: Most people don't realize that added abilities from mutate are copiable traits. If you put otrimi on this on turn 4 and make a copy, the copy will also have all benefits of mutation.
Have I missed any cards of particular note?
To put this into perspective
Blight Mamba was a 1/1 but then mutated its suddenly a 6/6
2 hit wonder
Shu Yun, the Silent Tempest WUR Voltron Control
Temmet, Vizier of Naktamun WU Unblockable Mirror Trickery
Ra's al Ghul (Sidar Kondo) and Face-Down Ninjas
Brudiclad, Token Engineer
Vaevictis (VV2) the Dire Lantern
Rona, Disciple of Gix
Tiana the Auror
Hallar
Ulrich the Politician
Zur the Rebel
Scorpion, Locust, Scarab, Egyptian Gods
O-Kagachi, Mathas, Mairsil
"Non-Tribal" Tribal Generals, Eggs
and it regenerates... barf.
While I can certainly understand the power of Mutate in infect colors, I can't help but think that ignoring evolve is the wrong way to ignore Otrimi. If you just want to use it as a reusable buff, you are using Otrimi as a worse Brokkos 99% of the time (paying 1 more for the initial cast is certainly worth never paying commander tax in my book). The only thing making Otrimi worth using over Brokkos is its interaction with mutate so ignoring that seems kind of silly.
With that said, it's totally possible that Brokkos is simply a better commander.
Silhana Ledgewalker/Slippery Bogle/Gladecover Scout cheap hexproof bodies
Yeah, just realized that last night. Whoops.
Also just realized that mist-syndicate naga is pretty excellent as traits/abilities gained through mutate are copiable traits... though it might not make sense to put Otrimi in front of the chain here due to legend rule problems.
Edit: List in OP edited with suggestions from thread.
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