Tafarihm, Tireless Writer

Whenever a permanent achieves its purpose, exile
cards from the top of your library until you exile
a card with an ability that allows the permanent
to achieve its purpose. You may cast it without
paying its mana cost. Put the exiled cards on the
bottom of your library in a random order.
Tafarihm's power is equal to the number of
permanents with abilities described above you
control.
When one story is complete, he takes a new sheet of
paper and begins writing another.