Spirit Tome of Croshaw

Spirit Tome of Croshaw enters the battlefield
with four Age counters on it.
At the beginning of your upkeep, you may
discard two cards. If you do, remove an Age
counter from Spirit Tome of Croshaw and draw
a card.
When there are no Age counters on Spirit Tome
of Croshaw, take an extra turn. Then shuffle
Spirit Tome of Croshaw into your library.