Witchstalker
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.
Christopher Moeller
The List (PLST)
• #M14-202Rulings
The counter will be put on Witchstalker before the spell cast by an opponent resolves.
(wotc • 2013-07-01)
If an opponent casts a copy of a card that’s blue or black during your turn (as opposed to putting a copy of such a spell directly on the stack), the ability will also trigger. Check for the word “cast” in the effect that creates the copy.
(wotc • 2013-07-01)
Rulings
The counter will be put on Witchstalker before the spell cast by an opponent resolves.
(wotc • 2013-07-01)
If an opponent casts a copy of a card that’s blue or black during your turn (as opposed to putting a copy of such a spell directly on the stack), the ability will also trigger. Check for the word “cast” in the effect that creates the copy.
(wotc • 2013-07-01)