Whenever one or more creatures are put into your yard from your library, you get to reanimate one, as a treat
One of things you mind find is that you have too many cards to fit in one deck
Like most Magic: The Gathering cards, the value of Summon: Bahamut depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (Final Fantasy)
You can't use Tenacious Tomeseeker's ability to return an adventurer card from your graveyard to your hand
This second, simpler ability represented the Minstrel's creation of hard bosses while also passively rewarding players for controlling Towns
For example, Final Fantasy 14 's Emet-Selch can transform into Hades whenever the player has 14 or more cards in the graveyard