Jace, Ravnica's Refuge

Whenever a creature card is put into your
graveyard from anywhere, you may have this card become a copy of that card, except it has
Jace, Ravnica's Refuge's abilities.
At the beginning of your upkeep, mill X, where
X is this card's toughness.
If this card would leave the battlefield while its
name is not "Jace, Ravnica's Refuge,", exile it,
then return it to the battlefield at the beginning
of the next end step.