Koihsa, The Dreamer

Koisha, The Dreamer enters the battlefield
tapped and doesn't untap during your untap step.
Whenever you cast a blue or a black spell, untap it.
{t}: Exile the top two cards of each player's
library, then choose one card among those. For
as long as that card remians exiled, you may look
at it, you may cast it, and you may spend mana as thought it were mana of any type to cast thas spell.
If there are ten or more cards exiled with Koisha, transform it.