Robert Baratheon, Usurper

Trample, armored 1
When Robert Baratheon, Usurper enters the
battlefield, you become the monarch.
At the beginning of your first postcombat main
phase, if Robert attacked the monarch this turn
and you are not the monarch, untap all creatures
you control that attacked the monarch this
combat. After this main phase, there is an
additional combat phase followed by an
additional main phase.