Mutate is a brand new mechanic in Ikoria: Lair of Behemoths. Creatures with mutate can be cast for their mutate cost to stack with a non-Human creature, Voltron style. It looks a lot like bestow, but the key part of mutate is that you can add the mutate spell to the top or the bottom of the stack. The entire stack is one big creature with the power and toughness of the top card and all the abilities of every creature in the stack.
It sounds a little bit wonky, so here's an example from the Ikoria mechanics article:
If you mutate your Cloudpiercer onto your Mosscoat Goriak, you can either have a 5/4 reach, vigilance creature that rummages or a 2/4 with the same abilities. In this case it's pretty obvious that you want the 5/4 version, but as you build a bigger, better monster you'll get to choose if you want the new stats or just the abilities.
There are two key things to note with mutate before I get into individual cards and their Standard applications. The first is that mutations don't create a new creature, even if you mutate on top. The entire stack functions as the same creature that was there before, just better now. This means that if the creature was summoning sick, tapped, or under the effects of something like Pacifism, all of those remain true. Conversely, this means enters-the-battlefield triggers won't happen, and you can mutate a bigger statline onto an existing creature and attack right away. The second is that when you mutate you trigger the "when this creature mutates" abilities of the entire stack, including the mutation you just added.
What happens if the mutate target dies before your spell resolves? Much like bestow, the mutate spell on the stack will just resolve into the normal creature. You won't get the creature's triggered ability from mutating, however. You didn't actually get to do any science, so your creation will not reward you.
When evaluating mutate cards, there are three main aspects to consider:
We want something big, impactful, and cheap. This sounds like any other creature in Magic, but it's extra important with mutate creatures because in many cases a lot of the power is built into the mutate ability. While most of the time this requires a creature already on board to suit up, you can also cast mutate creatures for their "front half" and then use cheap mutate costs to trigger them instead. This makes cheaper mutate spells especially powerful, because they're giving you access to much more than their own ability. This also makes tokens and cheap creatures themselves more powerful as they can provide the base creature to upgrade later.
With that in mind, all the mutate cards good enough for Standard fall into one of three major categories.
These are our big, Pacific Rim-level scary kaiju. These are largely expensive, well-statted creatures that have a huge impact when mutated. These are great as the top of any stack, but the real power of these comes from their triggered ability. I seriously could not believe the text on several of these when they were previewed.
Nethroi, Apex of Death is probably the single most powerful mutate creature if cost is no object. When this was originally previewed in Japanese I did not believe the translation. There's an awful lot you can do with just power 10 or less, and the mutate cost can be paid in just two colors.
Powerful cards that work well with Nethroi include (but are not limited to) Risen Reef, Yarok, the Desecrated, Agent of Treachery, Cavalier of Thorns, Thassa's Oracle, Fiend Artisan, Embodiment of Agonies, Gray Merchant of Asphodel, Sage of Mysteries, Arboreal Grazer, Cruel Celebrant, Teysa Karlov, Corpse Knight, and just about any of Standard's X-mana 0/0s like Stonecoil Serpent.
While the mutate cost is expensive but game-ending, the base creature is nothing to sneeze at. A five-mana 5/5 with deathtouch and lifelink is a very reasonable defensive body to buy you time. I'll definitely be building around Nethroi to try and break it in the next few weeks.
Snapdax, Apex of the Hunt has a relatively cheap, aggressive body. A 3/5 with double strike hits hard, and for just one more mana it comes with a Warleader's Helix. Being able to target planeswalkers is a huge deal and means that Snapdax on five is a huge board swing almost every time. This is a lot less flashy than Nethroi but still incredibly powerful.
Vadrok, Apex of Thunder is the cheapest in the Apex cycle. At just three mana, Vadrok is a great body to suit up and is almost in the enabler category, but the mutate trigger is absolutely incredible. For just one more mana you get up to three mana back immediately. Mutating Vadrok on turn four allows you to double spell for an unreasonable amount of tempo.
Vardok is probably going to be one of the most (if not the most) played mutate engines, as it becomes very easy to double spell every turn after you put Vadrok into play. Cast a two to three-mana spell, mutate onto Vadrok and recast that spell, rinse and repeat while continually upgrading your monster. We'll get to Sea-Dasher Octopus later on, but Vadrok and Sea-Dasher are a very potent combo.
Illuna, Apex of Wishes reads really well on first glance. Every time you mutate you basically get to cascade for a permanent. This is really powerful, but the first one costs you at least six mana, and a five-mana 6/6 flier is large but unexciting. Illuna might be held back by how expensive it is unless there's a solid mana engine behind it.
I almost didn't want to include this one, but Brokkos is the final member of the Apex cycle, and being able to mutate from the graveyard is upside. I don't see this making big waves, but Sultai decks in Standard already heavily use the graveyard, so this has a place if people want the effect.
Dirge Bat's mutate cost is pretty steep, but having flash makes this card much more powerful both as a mutate spell and as a creature to mutate onto. It's very easy to end-step a Dirge Bat and then untap and immediately mutate onto it, upgrading your Dirge Bat, removing an opposing threat, and giving you new abilities and another mutate trigger on top of that. This card is secretly very powerful, and I think the general public is sleeping on Dirge Bat.
Cubwarden is the most innocuous of the heavy hitters. A 3/5 lifelink is just "fine"—not exciting, mostly unplayable on its own. The big reason to play Cubwarden is that the mutate costs the same amount of mana as the body and comes with two extra 1/1s. It's not quite three bodies because mutating just upgrades an existing body, but in white aggressive decks Cubwarden is an excellent turn-four play that upgrades something small and gives you more tokens to pump up. Multiples of Cubwarden stack well, either by making four tokens or upgrading a token and making two more.
These are cards that aren't necessarily weaker, but the real strength of these mutate creatures comes from their mutate cost. Anything that costs three or less mana to mutate is a good deal, and things that cost two or less are a great deal.
Double green is a bit steep, but Gemrazer has a great set of stats and mutates for very cheap. Keep an eye on this one, it's not just a sideboard card. Getting a Naturalize is nothing to sneeze at, but the real strength here is mutating for three mana and being a good set of stats and abilities.
Unlike Gemrazer, Huntmaster Liger only needs a single white to mutate and works very well with cards like Cubwarden. Upgrading a small token and pumping your team is exactly what white aggressive decks are looking for, and the mutate cats are a great team in that regard. Huntmaster Liger is a bit less likely to see play in a dedicated mutate deck, but cheap enablers might be good enough to just play regardless of their ability.
Lore Drakkis mutates for very cheap, and the ability is incredibly strong. I expect to see a lot of this alongside Vadrok and potentially Illuna as a cheap way to repeatedly trigger mutate, but it's also powerful as just a rebuy on spells you've already cast. You do need a creature in play to get the rebuy, but two hybrid mana is a low, flexible mutate cost.
This is the most powerful enabler yet. Ninja of the Deep Hours, but the vanilla mode has flash and costs 1 less. Mutate triggers for just 1U. This is one of the best mutate cards we've got, and it's good even outside a dedicated mutate deck. Get your playset now, this is a good one.
There's a few cards that don't actually have mutate, but they mention the mechanic and are powerful synergy pieces.
Zagoth Mamba is a strong mutate target, but only against small creature decks. A 1/1 isn't much to write home about and -2/-2 won't kill much that costs three or more. That said, if you have Zagoth Mamba against Mono-Red or Mono-White and mutate it twice, they're going to be very far behind.
We want cheap mutate spells, and Pollywog gives it to us. No matter which mode you cast in, your mutate spells will cost one less and you'll get to loot every time you cast one. 1/3 is both a decently sturdy statline (that survives Stomp) and a nice body to mutate onto. This may look like a joke, but it's actually a mana dork for mutate with upside. Real card, I promise.
I'm not very sure of this one, but Crystalline Giant is an ever-growing list of keywords that makes for a very solid base for a mutate stack. If you ever hit hexproof in the first two turns you'll have a terrifying threat you can keep upgrading without worry. It's RNG, but I think the average creature you get in two triggers is reasonable enough to play anyway.
Mutate looks very powerful, and as soon as WotC spoils the land cycle I'll be building all sorts of Ikoria decks for Standard and Pioneer. Keep a close eye on my Twitter as we finish out the preview season because I plan to complete my usual 50-deck challenge.
Lastly, don't forget to tune in next Wednesday to the Ikoria Early Access event on Arena! It'll be streamed on Twitch with all your favorite content creators, including yours truly. Enjoy the previews, go nuts on deckbuilding, and wash your dang hands.