Sephiroth (voiced by George Newbern) is the embodiment of Cloud's darkness. He, along with Cloud, Tifa, Aerith, Yuffie, Zack, and Cid, originate from the Squaresoft game Final Fantasy VII, where he served as the main antagonist, Sephiroth was once one of the most strongest, and bravest from a group of warriors called, SOLDIER, created from the Shinra Electric Power Company. However, after learning about how he was created, he eventually began to hate everything, so much, he wanted to destroy everything. His ambition failed however, when he was defeated by Cloud Strife, and vanished into the darkness. Even though he was gone, Cloud's darkness, and fear, allowed him to come back, and became the legendary, One-Winged Angel. Sephiroth is the only Final Fantasy villain so far to appear in the Kingdom Hearts series. He is also Darkseid's 2nd son as well as Darkblade's mortal enemy.
- Sphiroth will make a cameo in Jeffrey, Jaden & Friends' Storm Adventures of Avengers: Age of Ultron.
- Sephiroth gets along well with his sister-in-law, Eris, since they're both evil, immortal, omnipotent beings. He is one of the fiercest and most powerful members of the Horde of Darkness.
- Sephiroth is one of the ultimate enemies in the Jeffrey & Friends' Adventures series and the Jaden's Adventures Series.
- Aaron will become Sephiroth's enemy in the Aaron's Adventures Chronicles.
- Sephiroth also has the most famous theme song ever created, "One Winged Angel".