Quillback Kavu

Stockpile {2} (Exile this card from your hand: It gains "{2}: Put a cache counter on this card." and "You may cast this card from exile as long as it has a cache counter on it with its cost reduced by {1} for each cache counter on it.")
Quillback Kavu enters the battlefield with a +1/+1 counter on it for each cache counter on it as it was cast.
Avoid its lair or risk a prickly death.