A young demon in her late teens. She had bright yellow skin and pink eyes. She had long scruffy red hair and pointed elf-like ears. She had a detachable tail and wore a skin tight purple outfit that resembled a one-piece swim suit.
Lyamon could hypnotize people and crawl along walls, she could detach and attack with her tail and had a poisoned tounge.
Lyamon was summoned by her Lord Zennon to try and kill Miki Makimura to get Devilman to surrender and return to the Demon Tribe. In a buzz of delight she awakens her brother to tell him of her proud task, and that she was going off to Kill Miki, after a warning from her brother to be careful she departs.
She eventually finds Miki and traces her for a while, which leads her to Nakado Academy. At the school she disguises herself as a human named Momoko Iwami, and hypnotizes the class before trying to poison Miki, but is interrupted and tries again later, this time having success sending Miki into a fever almost instantly. As Lyamon tries to make her escape however, she is seen by Devilman who chases her to the roof and causes her to fall of after a short battle.
He strips her near nude and ties her up, suspending her from a beam, he proceeds to whip Lyamon trying to get her to cure Miki but she refuses and calls for her brother to come and rescue her. He quickly arrives to see his sister bound and in pain, enraged he battles with Devilman but after a short fight he is defeated, with his dying breath he frees Iyamon from her bounds, she then goes to her brother and promises to avenge him. Leaping up, she tries to kill Devilman but is easily over powered and set alight, burning her alive. Devilman tries to get the cure from her one last time but Lyamon spitefully tells him there was no cure and dies. This however turned out to be a lie and Miki quickly recovers.
- Lyamon along with her brother Bau appear as henchmen of Jinmen and the Skull King in Shin Violence Jack. The two temporarily merge when fighting Violence Jack.
- Lyamon's origonal design was more gecko-like. She had a longer, thicker neck, sclaes across her body and a layer of fins going down her spine.
- Lyamon briefly appears in a chapter of the Go Nagai manga 'The Abashiri Family'. He appearence here uses the unused anime design.