The Mollusc, (or simply "Mollusc") is the main antagonist of Pac-Man: Adventures in Time for the PC. His origins, along with the reasons for his actions, are unknown.
It is shown to be a shadowy, elusive, isolated creature which has settled in a dark cave far from civilization. Mollusc speaks an unknown language in a deep menacing voice, which the ghosts, (namely Clyde and Inky,) seem to understand. It's head and hands are the only parts of it seen, as the rest of it is hidden in the shadows. It's eyes are an eerie white, and are large ovaline shape. It's mouth, (which spans about half the size of both it's eyes,) can be seen underneath.
PAC-MAN: Adventures in Time
The Mollusc's first (and so far only,) appearance has been in Pac-Man: Adventures in Time for the PC. He is seen in the intro sequence receiving the stolen "Artefact" from Clyde and Inky, who have stolen it under his command. The Mollusc smashes the artefact in an explosion sending the four pieces across time and space. Professor Pac-Man alerts Pac-Man of the danger, who then sets out to stop him via a time machine built by Professor Pac-Man. Pac-Man ultimately finds all four of the pieces of the Artefact, and returns to the present time to the precise moment after the Mollusc smashed the Artefact. Pac-Man fires a high-powered energy beam from the Artefact at the smitten Mollusc, disintegrating him, and prompting Inky and Clyde to flee the scene. Pac-Man triumphantly rises the recovered Artefact above his head, victorious.