① He forms the Organization using The World that Never Was as headquarters and Castle Oblivion as a research facility.
※Connects from Terra-Xehanort ④
-His intention in creating the Organization is to create 13 vessels of darkness and orders Xigbar and the others to collect new candidates. During this time he also sets Aqua’s armor under Ansem the Wise’s lab in the room of sleeping as well as has the Organization members search Castle Oblivion for the room of waking, in which Ventus’ body lays dormant.
② [KH1FM][Days] Finding Roxas who was birthed into Twilight Town, Xemnas initiates him into Organization XIII.
③ [KH1FM][KH2FM] He fights with Sora at Hollow Bastion, and afterwards converses with Roxas at the Dark Margin.
④ [COM] Using other members of the Organization to lure Sora to Castle Oblivion, he attempts to steal Sora’s memories in order to create a replica Keyblade wielder.
⑤ [Days] He orders Roxas and Xion defeat Heartless in order to create the Kingdom Hearts of People’s Hearts.
⑥ [Days] He orders Axel to retrieve Roxas and Xion who had tried to escape from the Organization.
⑦ [KH2] Along with other members of Organization XIII, he appears in Hollow Bastion before Sora.
⑧ [KH2] In The World that Never Was he faces off against Sora and friends, but not only is the Kingdom Hearts of People’s Hearts vaporized by Ansem the Wise, but Xenmas is also defeated by Sora and Riku.
※Connects to Master Xehanort ⑧
⑨ [KH 3D] He appears before Sora to combat and reveals the true intentions of creating Organization XIII. He is successful in wearing Sora out to the point where Sora can no longer wake up.
⑩ [KH 3D] He waits with the members of True Organization XIII for the arrival of Master Xehanort before vanishing.