Krex, Deathchant Champion

Deathtouch, protection from black and white.
When Krex enters the battlefield, sacrifice it
unless you pay 5 life.
Whenever a Knight dies, you may pay 3 life. If
you do, Krex deals 3 damage to target creature.
If a creature dealt damage this way would die,
exile it instead, and it's owner loses 3 life.