Tome of Forgotten Knowledge

Tome of Forgotten Knowledge enters the battlefield with three lore counters on it.
{x}{u}, {t}: Draw cards equal to the number of lore counters on Tome of Forgotten Knowledge, then remove a lore counter from it. X is equal to the
number of lore counters on Tome of Forgotten Knowledge.
When there are no lore counters on Tome of Forgotten Knowledge, destroy it.