War of the Spark

Bioessence Hydra | Creature | Hydra Mutant | Trample Bioessence Hydra enters the battlefield with a +1/+1 counter on it for each loyalty counter on planeswalkers you control. Whenever one or more loyalty counters are put on planeswalkers you control, put that many +1/+1 counters on Bioessence Hydra. | Mathias Kollros

Merfolk Skydiver | Creature | Merfolk Mutant | Flying When Merfolk Skydiver enters the battlefield, put a +1/+1 counter on target creature you control. {3}{G}{U}: Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.) | Sara Winters

Roalesk, Apex Hybrid | Legendary Creature | Human Mutant | Flying, trample When Roalesk, Apex Hybrid enters the battlefield, put two +1/+1 counters on another target creature you control. When Roalesk dies, proliferate, then proliferate again. (Choose any number of permanents and/or players, then give each another counter of each kind already there. Then do it again.) | Svetlin Velinov

Niv-Mizzet Reborn | Legendary Creature | Dragon Avatar | Flying When Niv-Mizzet Reborn enters the battlefield, reveal the top ten cards of your library. For each color pair, choose a card that's exactly those colors from among them. Put the chosen cards into your hand and the rest on the bottom of your library in a random order. | Raymond Swanland