Merloo is one of the Four Sages in the Tribe of Ancients. The other three sages are Merlight, Merlimbis, and Merlumina. Not much is known about Merloo, because you do not see the character in any game. There is a stain-glass picture of the four sages in the Mirror Hall connecting Flipside and Flopside. Tippi or Tiptron's tattle reveals that Merloo was a very wise man. Merloo is thought to have written the Light Prognosticus long ago before the Tribe of Ancients collapsed. Merloo is not proven to be distantly related to anyone in either Flipside or Flopside.
Merloo is also said by Tippi and Tiptron that he is a powerful, dimension-controlling magician. Because Dimentio is also a powerful, dimension-controlling magician, some believe that Merloo and Dimentio might be related.