Ikoria: lair of Behemoths

Mutate Creatures
As a whole, the mutate mechanic is an extremely interesting mechanic and an entire cubelet could be designed around mutate containing one copy of all the mutate creatures and additional spells to round out the experience. Any creature listed here would likely be the only mutate creature in the deck, so its effect is only going to normally happen once in a game.

Luminous Broodmoth
A powerful mythic that adds resiliency to one player. Will likely make them the target until Broodmoth is removed from the game.

Mythos of Snapdax
A unique boardwipe that puts all the power into the caster's control as you will always have the ability to choose.

Mythos of Illuna
Copy spells that fight could create a unique experience.

Sea-Dasher Octopus
If cards like Looter Il-Kor are annoying, but you want a similar effect, this would be a good substitute.

Extinction Event
A unique boardwipe that also exiles, which can be essential.

Heartless Act
A removal spell with options.

Mythos of Nethroi
Three-mana remove any nonland permanent is very fair and acceptable in Cubelet.

Mythos of Vadrok
Neat way to force through damage when the board stalls. It lasts until your next turn, which adds extra politics to the game.

​Gemrazer
Artifacts and enchantments can be very annoying and this could be great to keep them in check.

Mythos of Brokkos
Usually tutors are frowned upon, so this mythos is not necessarily approved for cubelet, but you are welcome to try it.

Boneyard Lurker
A gravedigger grabbing a permanent is a fair card.

Brokkos, Apex of Forever
Shared graveyard makes this card very interesting if it ever ends up in the graveyard.

Chevill, Bane of Monsters
Not powerful, but can add a fun subgame for the player that casts Chevill.

Lore Drakkis
If you are looking for a Snapcaster like effect, this could be a great solution. It is not the same as Snapcaster Mage, but it works.

Skycat Sovereign
Great mana sink for the late game when you are trying to get those last few points of damage.

Crystalline Giant
Adds a unique subgame and adds an artifact to the deck for those that play delirium.