Timewall

Whenever your opponent attacks, you may put a
doom counter on target creature and on
Timewall. If Timewall has reaches five or
more doom counters, sacrifice it.
{2}, Remove 1 doom counter from target:
Deal 3 damage to it.
{1}, Remove 2 doom counters from target:
Put three -3/-3 counters on it.
{t}, Remove 3 doom counters from target:
Exile it, draw two cards and add {c}{c}.