Somlum is a Zoanoid created by Dr. Hamilcar Barcas of the Chronos Corporation. He is a Lost Number: a Zoanoid that has lost its reproductive value during the optimization process, and so can never be duplicated. He appears in both animated Guyver series along with fellow Lost Numbers Aptom and Dyme.

Somlum possesses great agility and is capable of discharging an organic adhesive from his beak, which merges with any biological entity it touches. When the Lost Numbers confront Sho Fukamachi, Somlum uses his bio-glue to fuse the Guyver's arms together. The Guyver tears himself free in spite of wounding himself in the process and uses his vibration blade to cut Somlum down.

In the Guyver TV series, Somlum is blasted by Sho's Mega-Smasher and annihilated.