“A loathsome parasite that inhabit Lost Izalith. It is completely immobile, yet still lives. When worn on the head, it emanates blinding light, which is why it’s known as a Sunlight Maggot.”
The Sunlight Maggot is obtained as a drop from the red-eyed Chaos Bug, a unique mob that is found past the shortcut door separating the Demon Ruins from Lost Izalith (opening the door requires “Chaos Servant +2”) or by going behind the Titanite Demon in Lost Izalith. There are total of 9 Chaos Bugs on both sides of the shortcut door. The Sunlight Maggot can only be received once per playthrough, since the red-eyed Chaos Bug will not respawn. It can also be obtained by killing Solaire of Astora, if the red-eyed Chaos Bug has not been killed before speaking to him after killing the Centipede Demon.
The Sunlight Maggot emanates light when worn as a helmet, making it useful for exploring dark areas such as the Tomb of the Giants. It cannot be upgraded, however, and offers poor physical defense and resistances (with the exception of very high fire resist), limiting its utility to exploration. It can be used as an alternative to the Skull Lantern, as it does not sacrifice the ability to block, and does not have to be cast like Cast Light.