The boss of the Armor Spider Archstone.
"Since ancient times, a fire demon has been sealed in an underground temple filled with dragon bones."
The archstone speaks of a fire Demon which has been trapped in the Temple with Dragon God since ancient times, Flamelurker is undoubtedly related to that fire Demon. Little can be extrapolated about Flamelurker's origin since the boss soul is given to Ed, and is not used to create any spells.
A ten foot tall, horned creature covered in spikes and engulfed in flames. Its fist attacks create huge explosions of fire. Trapped deep inside the Stonefang Tunnel, the Flamelurker is a hulking humanoid demon completely covered with fire with powerful claws capable of emitting energy shockwaves. It can also leap for a very long distances to hit it's target with a double hand smash. It usually roars before it attacks and, when wounded, jumps back, leaving fiery footprints in front of him.