The elk ability on
Oko, Thief of Crowns is
incredibly dangerous. He is or will soon be the newest EDH bogeyman.
My hope is that the EDH RC decides Oko interacts poorly with the format and bans Oko. I don't know if he'll warp the format, but I feel he interacts with it poorly approximately the same way
Karakas does, simply by making commanders irrelevant repeatedly for a trivial investment.
Over on Scryfall
we've catalogued the swap removal cards. There's two types: either the card removes the target from the battlefield and replaces it with a token (like
Beast Within) or it is an aura (like
Darksteel Mutation). Oko is the singular exception: his card is a one-shot effect that stays true forever.
The ones that remove the target from the battlefield are just spot removal or wipes with a trade; you can simply choose to do nothing and you'll be able to get your commander back later. The auras require you to actively do work to protect or restore your commander: you must either remove the aura or find a way to remove your commander from the battlefield (spot removal, board wipe, flickering). This means the aura is a better way of taking a commander out of the picture long-term, but players can still do something to reverse it. Oko's range of responses is narrower still than the aura approach: it's like an aura, but there's no actual aura to remove, so the only option is to remove your commander from the battlefield somehow.
Also, of all of them, Oko is the only one that's trivially repeatable. Once I use my
Darksteel Mutation on your commander, I can't also Darksteel Mutate something else: my aura's played and out of my hand. With Oko, I can just elk commanders turn after turn, even while ticking up loyalty! Once you remove my
Darksteel Mutation I have to do some work to get it back and probably won't get it back right away; once you reset your elked commander I can just Elk it again the very next turn. This means you can't
just reset your commander, you have to
also remove my Oko. (I can, of course,
Copy Enchantment the Darksteel Mutation to get one extra use, but I can also
Spark Double my Oko to double my repeatable capacity.)
So. He's hands-down the most effective swap removal option ever seen: he's got the narrowest range of responses available;
and he's trivially repeatable;
and you have to remove two things, not just one. He's simply the most effective card at making players' commanders irrelevant for the rest of the game, and if Oko's player can wall up for a couple of turns he can do this to everyone's commander and keep it that way. And he's at CMC 3!
Everyone should be packing spot removal, but Oko drains more spot removal than the other options. Everyone should prepare that they may not be able to make much use of their commander during the game, but Oko makes this more likely to be true and stay true for the lowest resource investment of all other cards I can think of.
It's not even the only ability on the card, so when the player has nothing more to Elk, Oko's still useful in other ways. He's in Simic, meaning it's not even colors people will be unhappy to play: traditionally they're the two most powerful colors to have in an EDH deck anyway. It's not like he's Boros colored.
So, yeah, Oko's incredibly dangerous.