Essence Aegis

You may play Essence Aegis anytime you could
play an instant for {g} instead of its normal
casting cost. If you do, it loses "Return Essence
Aegis to its owner's hand at end of turn" and
gains "Sacrifice Essence Aegis at end of turn."
If any creature you control would be exiled from
play, put a +1/+1 counter on it and it gains
Trample until the end of your next turn instead.
Return Essence Aegis to its owner's hand at end
of turn.