Witchstalker {1}{G}{G}
Creature — Wolf
Hexproof (This creature can't be the target of spells or abilities your opponents control.)
Whenever an opponent casts a blue or black spell during your turn, put a +1/+1 counter on this creature.
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Cards that do something similar expected a card that isn't here?
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Mold Adder 96%
$0.14#14313
"Whenever an opponent casts a blue or black spell, you may put a +1/+1 counter on this creature."