Jethro, Faithful Ass

Partner with Caulder, Faithful of Bahamut
(When this creature enters the battlefield, target
player may put Caulder into their hand from their
library, then shuffle.)
Hexproof, protection from colors
If Caulder, Faithful of Bahamut leaves the battlefield because of a spell, ability, or damage
caused by an opponent, transform Jethro,
Faithful Ass.