Did you ignore the rest of the post?
no no i did not lol

Further, Ultimecia's Witch Embodiment powers granted her the ability to reach into other's minds and pull things out (as she often displays when completely removing a character's stock of a certain type of Spell). In the case of Griever, she simply manifested the thoughts she pulled from Squall's mind regarding what he believed to be the most powerful being in existence. This would be a great strategical move on Ultimecia's part.
this part was said by another forum member and as such is his or her take on things and not actualy evidence

This is made even more plausible when examining what the japanese version has Ultimecia say:

Ultimecia: Your feelings, I shall summon the most powerful of things [from them]! The more strongly you feel, that will be what shall torment you. Fufu.
hmm well since that actualy is in the game its pretty hard to refute and i can see how you might think that
slightly anyway
but it still doesnt necessarily apply to griever
basicly im still not buying lol