The Esper Mateus from Final Fantasy XII is named after, and based on, the Emperor, its appearance resembling the Emperor's armor. The Esper's back story is based on his command of hell. The Totema Mateus from Final Fantasy Tactics Advance is also named after the Emperor, but that is where the similarities end.
Dissidia Final Fantasy (2008)
As one of the higher-ranking villains, the Emperor is the mastermind of the game's overarching plot to destroy Cosmos and drown the world in darkness. He manipulates hero and villain alike towards this goal and it is later revealed the Emperor orchestrated the plan with the intent for both Cosmos and Chaos to die. Having manipulated Jecht into fighting Tidus when the former was a Warrior of Cosmos in a previous cycle, he has obtained a Crystal from Jecht's fighting attuned to Chaos instead of Cosmos. The Emperor's ultimate goal is for both gods to perish and their warriors with them, leaving him to survive their destruction due to the power of his Crystal and rule over existence unopposed.
His alternate outfit is a pale purple, gray and white palette swap based on his appearance in an alternate Yoshitaka Amano artwork.
The Emperor is a Warrior of Chaos who is the one responsible for Tidus being summoned to fight Jecht, but Tidus's memories are stirred by Yuna. The Emperor attempts to kill her but Tidus protects her, leaving the Emperor to fight Yuna while Jecht tends to the wounded Tidus. During the battle Jecht transfers his light to Tidus, leaving himself an empty husk, and the Emperor enacts his plan to seize a Crystal by taking him to Chaos to be imbued with the power of discord. The Emperor later participates in the final battles, battling Yuna.
The Emperor's second alternate form is his Final Fantasy Origins appearance as seen in the Final Fantasy II opening cinematic, giving him a dark purple and black robe. As a bonus fourth outfit available for download from the PlayStation Network, the Emperor dresses in a gold and purple robe as the Emperor of Arubboth.
On March 7, 2017, the Emperor was shown in a livestream.
The Emperor is a boss-type enemy, and makes his playable debut as the representative antagonist of Final Fantasy II, unlocked by collecting Dark Crystal Shards.
The Emperor appears as a boss in Final Fantasy All the Bravest.
The Emperor is a boss in select FF II dungeons and a playable character who could be initially recruited during the Challenge Event where he could be obtained as a First Time Reward for completing the event's Rebel Hideout stage on Classic difficulty.
The Emperor appears as a vision and optional playable character. A 5-7★ Rare Summon, he has been available for summoning since the event The Dreadnought. His job is listed as Emperor, and his role is Magic Damage. His Trust Master reward is the Mateus's Malice rod.
The Emperor appears as an ability card in Mobius Final Fantasy.
The Emperor appears in Final Fantasy Trading Card Game as Dark- and Ice-elemental Backup and Forward cards.
The Emperor appears on a Triple Triad card in the version available via Final Fantasy Portal App.
Puzzle & Dragons
The Emperor appeared in Puzzle and Dragons as part of the Final Fantasy Collaboration in his Dark Emperor incarnation (which was largely derived from its original Famicom sprite design). The collaboration event happened in the North American version of the game from 2 to 15 November 2015.
Yo-kai Watch: Wibble Wobble
The Emperor appeared in the Dissidia Final Fantasy collaboration event as a Rank SS Yo-kai of the Shady Tribe.