The Lost Caverns of Ixalan

Sovereign Okinec Ahau | Legendary Creature | Cat Noble | Ward {2} Whenever Sovereign Okinec Ahau attacks, for each creature you control with power greater than that creature's base power, put a number of +1/+1 counters on that creature equal to the difference. | Victor Adame Minguez

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