Zuko, the Dishonored

Banished Prince: If Zuko, the Dishonored would
die, banish it to exile instead.
Whenever Zuko enters the battlefield, you may
search your library for an Avatar creature card
and put it into your hand. As long as you control
one or more Avatars, Zuko has indestructible.
Whenever an avatar leaves the battlefield, Zuko
the Dishonored deals 3 damage to its controller
unless that player pays {1}.