Darth Bane, The Last Survivor

Whenever Darth Bane, The Last Survivor deals
combat damage to a player, untap each creature
you control. After this combat phase, there is an
additional combat phase. Darth Bane can't attack
a player it has already attacked this turn.
Bane recognized that Sith infighting had weakened
them to the point that the Jedi could destroy them.
To rectify this, Bane reformed the Sith and created
the Rule of Two, mandating that there could be only
two Sith — a Master and an apprentice.