Ikoria: Lair of Behemoths

Cubwarden | Creature | Cat | Mutate {2}{W}{W} (If you cast this spell for its mutate cost, put it over or under target non-Human creature you own. They mutate into the creature on top plus all abilities from under it.) Lifelink Whenever this creature mutates, create two 1/1 white Cat creature tokens with lifelink. | Kekai Kotaki

Dirge Bat | Creature | Bat | Mutate {4}{B}{B} (If you cast this spell for its mutate cost, put it over or under target non-Human creature you own. They mutate into the creature on top plus all abilities from under it.) Flash Flying Whenever this creature mutates, destroy target creature or planeswalker an opponent controls. | Paul Scott Canavan

Everquill Phoenix | Creature | Phoenix | Mutate {3}{R} (If you cast this spell for its mutate cost, put it over or under target non-Human creature you own. They mutate into the creature on top plus all abilities from under it.) Flying Whenever this creature mutates, create a red artifact token named Feather with "{1}, Sacrifice Feather: Return target Phoenix card from your graveyard to the battlefield tapped." | Lie Setiawan

Gemrazer | Creature | Beast | Mutate {1}{G}{G} (If you cast this spell for its mutate cost, put it over or under target non-Human creature you own. They mutate into the creature on top plus all abilities from under it.) Reach, trample Whenever this creature mutates, destroy target artifact or enchantment an opponent controls. | Svetlin Velinov

Frondland Felidar | Creature | Cat Beast | Vigilance Creatures you control with vigilance have "{1}, {T}: Tap target creature." | Steve Prescott

Umori, the Collector | Legendary Creature | Ooze | Companion — Each nonland card in your starting deck shares a card type. (If this card is your chosen companion, you may put it into your hand from outside the game for {3} any time you could cast a sorcery.) As Umori, the Collector enters the battlefield, choose a card type. Spells you cast of the chosen type cost {1} less to cast. | Jehan Choo