Kassadin, The Void Walker

Menace
Whenever Kassadin deals combat damage to a
player; you gain 1 life, draw a card.
Whenever Kassadin becomes blocked: add
{p/w}{p/w} to your mana pool until end of turn.
{3}{p/w}{p/w}: Put a -1/-1 counter on target creature
that blocked this turn.(once per turn.)
Kassadin is considered a white permanent.