Its based on norse, all the other games are based onto Midgard, as each game thrives over over to name the games world as "Midgard"
In some games from namco, in their Tales games (Tales of Phantasia, Tales of Symphonia) have summon spirits. In final fantasy 7, its almost like summon spirits but called aeons and etc...The definition is clear that it's definition can not be defined as game producers change the ideas of midgard and calling it clear.
If you want the most clearest definition of midgard, it would be best to search up the oldest game with the world of midgard which i think would be Tales of Phantasia
Fredji! Quick let us retreat to Midgard.
One of the three realms of Dark Age of Camelot.