Caesar, Helm of the Legion

Whenever another creature enters the battlefield
under your control, you may put a -1/-1 counter
on target creature. If you control that
creature, draw a card and lose 2 life.
Creatures you cast cost {1} less for each -1/-1
counter on creatures you control.
Sacrifice another attacking creature:
Caesar, Helm of the Legion gains indestructible
until end of turn.