The keeper of the crossroads, much like Papa Legba from real-life voodoo lore. A shrine to him can be found in the Voodoo Lady's shack in Tales of Monkey Island. His name is Ron Gilbert's name, the creator of the series, spelled backwards.
It's never confirmed but highly suggested that he is the mysterious Galeb, who is met in Episode 5 of Tales and is also based off of Papa Legba (note how their names are the same with the letters switched around, just like Nor Treblig and his namesake) in voodoo mythology.