Letter game: RE

Rufus Shinra (FF7)

Shiva

Most summons are also bosses right?

Yup, you can fight Shiva in the bonus dungeon of , IV, V, VI, an optional boss in X, X-2, and XII: RW.

Tiamat from various games.

Am I allowed to use The Undying as a whole from FFXIII for a U?

Yes, I guess.

Vormav (FFT)

warlord Rojgnoj

Xande (FF III)

Yunalesca!
I had no idea what topic to play next, so I thought let the other ones take Z :p

Zemus or Zeromus

Let's try.......Final Fantasy locations (towns, worlds, continents, dungeons, etc.)

Ancient Forest (FF7)

B has a few. We'll go with Bran Bal for the double whammy.

EDIT: Oh, yes, and the game. FFIX that was.

Calm Lands (FFX)

Doma Castle from FF VI

Elfheim
ff1

Fynn (FFII)

Gran pulse - XIII