Khurgo and Xarxes

First Strike, deathtouch
Whenever Khurgo and Xarxes attacks for the
first time each turn, untap all creatures you
control. After this phase, there is an additional
combat phase.
If this is not your first combat phase this turn,
Khurgo and Xarxes loses deathtouch, gains
menace, and assigns combat damage equal to its toughness rather than its power.