Assassin of Truth

Planeswalker slayer (If this creature would deal
damage to a planeswalker, it deals double that
damage to that planeswalker instead.)
Whenever a loyalty counter is removed from a planeswalker an opponent controls, put a +1/+1 counter on Assassin of Truth.
Remove a +1/+1 counter from Assassin of Truth:
Put a loyalty counter on target planeswalker.