The Seed Crystal is a giant, sentient crystal from legends of old, returned to Vana'diel to bring about the apocalypse and return it to Paradise.
It is the final boss of Final Fantasy XI: A Crystalline Prophecy - Ode of Life Bestowing. It spends a much of the story possessing a younger incarnation of Aldo and causing the amnesia of his sister. It rests upon the Stellar Fulcrum atop Delkfutt's Tower. It remains stationary in the middle of the battlefield during the course of the fight. It is immune to most enfeebling effects, although Dia, Bio, and Stun are effective. It has high magical and moderately high physical defense. It also has a draw-in effect and a Regen effect that cannot be dispelled. Seed Crystal's normal attacks are magical and cannot be absorbed by Utsusemi or Blink.