Sothis

Sothis (, Sothis) is a character who debuts in Fire Emblem: Three Houses, as an entity that appears in Byleth's dreams and eventually manifests into a human form. In Super Smash Bros. Ultimate, she appears in Byleth's Final Smash as well as their reveal trailer.

Origin
Sothis is the progenitor god of the continent of in . Many years before the start of the game, Sothis arrived in Fódlan and created her children, the ns, as well as gifting the humans who already lived on the continent, the ns, with great power and technology. Eventually, the Agarthans became greedy and arrogant and attempted to wage war against Sothis and the Nabateans, only to nearly destroy themselves and the continent. Sothis expended most of her energy to heal the continent, then fell into a long slumber, while the surviving Agarthans retreated underground.

The Agarthans eventually recruited a bandit named to enact revenge on Sothis and the Nabateans. Nemesis and his warriors, the, slaughtered the sleeping Sothis as well as almost all of the Nabateans, using their hearts to grant themselves s and their bones to create the. The five surviving Nabateans, led by Sothis's daughter, allied themselves with one of Nemesis's own and eventually destroyed Nemesis and the Ten Elites. Following the war, Seiros rewrote history to hide the truth of the Heroes' Relics and Crests, creating the Church of Seiros. By the time of the game, Seiros has taken on a new identity, serving as the Archbishop.

Rhea plots to revive Sothis, bestowing Sothis's Crest, the, upon a woman of the church. The woman, whose name is Sitri, falls in love with and marries, the captain of the Knights of Seiros, and becomes pregnant; however, the child is stillborn. Sitri pleads with Rhea to use her Crest to revive her child and Rhea relents, killing Sitri in the process, though the baby remains without a heartbeat. Suspecting Rhea is not telling him the full truth of what happened to his wife and child, Jeralt fakes his and the child's death and flees the Monastery. This child grows up to be Byleth, seeing Sothis in their dreams; however, Sothis cannot remember her past. With Sothis's help, Byleth gains the ability to rewind time.

After a chance encounter results in Jeralt and Byleth being brought back to the Monastery, Rhea continues her plan to revive her mother. Sothis slowly regains her memories and eventually realizes that she is the progenitor god, but is forced to merge her power with Byleth in order to allow them to escape a dark realm they were banished to by one of the remaining Agarthans. Although Byleth now has the full power of the goddess, Sothis no longer appears to speak to them. Rhea attempts to have Sothis take over Byleth's body by having them sit on the throne, but Sothis refuses.

It is possible for Byleth to fall in love with Sothis and select her as their S-Support at the end of the game, even in Crimson Flower, despite Byleth's crest being destroyed in the route; should these conditions be met, Sothis will regain her form in Byleth's dreams.

In a similar vein to Viridi from the universe, Sothis has informal oldman-like speech pattern in the Japanese version.

In Super Smash Bros. Ultimate
Sothis appears as part of 's Final Smash, Progenitor God Ruptured Heaven. Additionally, one of Byleth's costumes uses the same color scheme as Sothis.

Spirit
Sothis also appears as a Legend-class support spirit in the Fire Emblem: Three Houses DLC Spirit Board.

Sothis uses a female Byleth puppet fighter whose alternate costume is based on Byleth after fusing with Sothis, and is fought on the Spear Pillar stage's Ω form. During the battle, the female Byleth will suddenly have a Final Smash. Also, the female Byleth's health will increase significantly when she is at high damage, referencing the first meeting between Byleth and Sothis after the former took a fatal attack from the bandit leader Kostas, where Sothis granted them the Divine Pulse, a time manipulation power which allowed Byleth to rewind time and disarm Kostas.

Other
Byleth's reveal trailer features Sothis all throughout, in a replica of the end of Chapter 10 from Fire Emblem: Three Houses.

Trivia

 * One of Sothis' lines from 's reveal trailer, "I see. Too many swordsmen, are there?" (, What? "No need for another swordfighter because there are already enough," you say?) may be a reference to arguments regarding the rapidly increasing amount of playable swordfightersーincluding, perhaps most notably, the Fire Emblem charactersーin both SSB4 and Ultimate, compared to the games up until Brawl.
 * Shortly after Byleth's reveal, the line itself has become notorious and memetic within the fandom, resulting in Sothis' English voice actress, Cassandra Lee Morris, replying to the fans as an acknowledgement of the line's infamy.
 * Sothis shares her voice actress with Morgana in English, who similarly narrated a DLC fighter's reveal trailer (in this case, ).
 * Sothis is the second character to hold a Smash Invitation in a character trailer without becoming a playable fighter, behind.