Snowball

When Snowball enters the battlefield,
it fights up to one creature you don't control.
Haste
{r}: Snowball gets +1/+0 until end of turn.
Whenever a source deals damage to Snowball,
that source's controller gets a revenge counter.
{1}{u}{r}, {t}: Snowball deals damage to target
player with a revenge counter equal to its power.
Whenever Snowball deals damage to a player,
draw a card.