Undyne The Undying

+2: Deal 2 damage to all creatures you don't control.
0: Until end of turn, Undyne The Undying becomes an 8/8 Merfolk Soldier creature with indestructible and double strike that's still a planeswalker.
-10: Deal 8 damage to target player and all permanents they control. You get an emblem with "creatures you control get +2/+2 and and first strike."