Jeriah, Ursine Unleashed

Trample
Whenever Jeriah, Ursine Unleashed attacks, exile
the top three cards of your library. Until the end
of turn, you may play those cards, and you may
spend mana as though it were mana of any color
to cast them.
At the beginning of each upkeep, if a player cast
two or more spells last turn, transform Jeriah,
Ursine Unleashed.