Lazav, Azorius Mastermind

Hexproof
Whenever a creature card is put into an
opponent's graveyard from anywhere, you
may exile Lazav, Dimir Mastermind and return to
the battlefield under your control as a copy of
that card, except its name is Lazav, Dimir Mastermind, it's legendary in addition to its other types, and it has hexproof and this ability.