A ruthless cat like alien from planet Magma responsible for the destruction of Ultraman Leo's home planet L77 of the Leo constellation, a neighboring galaxy near the Ultra Nebula M78, the home of the Ultras.
Alien Magma destroyed L77 with his twin pet monsters the Gillas brothers and aims to take over Earth by it starting with Japan. He and his monsters were the ones to show that Ultraman Leo will be a serious season not only by showing casualties of the floods they're making, but by also breaking one of the veteran hero Ultraseven's legs.
He may have been a serious threat at first, but when he returned many episodes later after Leo decapitated the Gillas brothers so is he not interested in taking over the world, but to marry Alien Rolan who's supposed to be the most beautiful in the universe (though looking at her so am I not sure if she can actually be considered beautiful due to Tsubaraya reusing parts from tough looking aliens) and harassing kids by stealing toys that the beautiful alien had made.
Some version of Alien Magma would appear in later series like in Mebius where two of them together with Fisherman Valky attempted to conquer Earth by riding down on a meteor, but the three got slain by an alien swordsman named Zamusha.
Another Alien Magma appeared in Ultraman X where he together with Alien Shaplay was hired by the conqueror Mold Spectre and his sister Gina Spectre to use a phenomenon called Dark Thunder Energy to revive the Spark Dolls that Xio are keeping into mad beasts and bring Mold's army from his own world.
