Final Fantasy 16’s interpretation of Sleipnir marks a great change in the franchise regarding the classic summon known as Odin. Sleipnir is a recurring character in Square Enix’s classic RPG franchise, and its first main appearance was with Final Fantasy 3, as the two first games in the series did not feature any sort of summon. The same is true for Odin, who was also introduced in the 1990 title. Nowadays, summons are a regular and important part of most games in the franchise and, in FF16’s case, central to the entire story and core gameplay structure.
https://screenrant.com/ff16-sleipnir-final-fantasy-change-odin-human-form/