Mavolia (Makai or Demon Realm in Japan) also known as Anise's Stockade is a reoccurring location, or rather realm mentioned in the Mana series. It is inhabited by the Mavole/Demons and is the source of the Echoes corrupting the Mana Tree which spawn the Thanatos (servants of the Echoes) who create the Grimslies in Dawn of Mana. In Heroes of Mana it was stated that Mavolia came to be due to Anise's curse against Mana. Mirage Garden is probably located on this world. It is known as the Underworld, and in fact many of the early Mana games simply called it just that while leaving the actual name of the Underworld out, most likely because consistent localisation/translation did not really exist in the Mana series up until Sword of Mana, upon which they added the name Mavolia onto its Underworld title which was likely in order to distinguish it from the other Underworld known as Hell (Jigoku in Japanese which literally means Hell AKA the Afterlife of Sinners), which is mentioned by Stroud as a place he plans to subjugate from Mavolia (alongside Fa'Diel and Paradise).
Instead of Mana the power of Mavolia is Psi originating from the creator of Mavolia: Anise the Witch and seeks to destroy Mana in every world in existence due to her hatred of Mana.
It only appears directly in the Remake of Trials of Mana under the name Anise's Stockade(which considering Mavolia is otherwise only known as the Makai/Demon Realm is it's true name in Japan) on the map though is referred to as Mavolia everywhere else in the game.