Derov, Majesty of the Savage

Trample
As long as you control creatures with total
power 20 or greater, Derov is indestructible.
Whenever a creature you control with power
4 or greater attacks, draw a card. If it's a
creature card, you may reveal it. If you do,
that attacking creature gets +X/+X until end
of turn where X is the revealed creature's
power.