This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
Mairu (Basque mythology)
Mairu, also called Maideak, Mairiak, Saindi Maidi (in Lower Navarre), Intxisu in the Bidasoa valley are creatures of Basque mythology. They were giants who built dolmens or harrespil. Like the dolmens, they are only found in mountains. They are often associated with lamia, though these are known in all the Basque Country.
The masculine counterpart of the lamia is the mairu. They are often described either as giants or as human sized but possessing immense strength. In this, they are comparable to the spriggans of Cornwall. The origin of the Mairu is thought to be as old as the "mouros encantados", who are thought to be the remnant of old pre-Roman deities.