The Lost Caverns of Ixalan

Deepfathom Echo | Creature | Merfolk Spirit | At the beginning of combat on your turn, Deepfathom Echo explores. Then you may have it become a copy of another creature you control until end of turn. (To have this creature explore, reveal the top card of your library. Put that card into your hand if it's a land. Otherwise, put a +1/+1 counter on this creature, then put the card back or put it into your graveyard.) | Matt Stewart

Squirming Emergence | Sorcery | | Fathomless descent — Return to the battlefield target nonland permanent card in your graveyard with mana value less than or equal to the number of permanent cards in your graveyard. | Simon Dominic

Palani's Hatcher | Creature | Dinosaur | Other Dinosaurs you control have haste. When Palani's Hatcher enters the battlefield, create two 0/1 green Dinosaur Egg creature tokens. At the beginning of combat on your turn, if you control one or more Eggs, sacrifice an Egg, then create a 3/3 green Dinosaur creature token. | Aaron Miller