Undyne,The True Heroine.

First Strike, Vigilance
Whenever you cast an instant or sorcery spell
Undyne The True Heroine gets +1+0 until end
of turn.
If Undyne would be dealt damage instead remove
that damage and put a undying counter on her.
She gets +1-1 for each undying counter on her.
When the 3rd counter is put on, transform
her.