Barnacle is a mutant with the ability to initiate a chemical reaction that solidifies moisture into a hardened shell. Barnacle most often uses this power to provide himself with a seemingly indestructible armor, encase others within a constrictive carapace, or spray a stream of hardened barnacle-like crust.
Barnacle was amongst the group of Acolytes that attacked the X-Men following Magneto's threat to launch an electromagnetic pulse that would bring human civilization to a standstill. Barnacle attacked the weather-manipulating X-Man named Storm in an attempt to play off her claustrophobia by encasing her in a hardened shell, but he was defeated by the indigo-skinned teleporting X-Man Nightcrawler.
Barnacle later reappeared as one of the renegade Acolytes who were assisting the Carrion Cove rebellion against Magneto's rule of Genosha. After the destruction of the island nation by the giant mutant-hunting robots known as Sentinels, Barnacle's final fate is unknown.