The Light Presence is a spiritual creature that is gentle, helpful, and has the ability to heal, rather than destroy, such as its counterpart the Dark Presence. Its main goal seems to be to end the Dark Presence, and protect Bright Falls and possibly the world from it. The Light Presence helps Alan Wake as he battles the Dark Presence to save his wife. Alan seems to be able to control the Light Presence, giving his flashlights the ability to shine brighter and the light to heal his wounds.
The Light Presence is controlled and possibly in the form of the spirit of a poet named Thomas Zane, who fought the Dark Presence in the 70s. Zane would write things, and the Dark Presence would bring the things he wrote to life. Zane lived a happy life with his muse and girlfriend, Barbara Jagger, on Bird Leg Cabin in Cauldron Lake. But one day, tragedy struck. Barbara went swimming down in Cauldron Lake and drowned beneath the waves.
Zane, struck with insanity and grief, was met by the Dark Presence. The Dark Presence tricked Zane into writing it a story in which it grew stronger and more powerful. And in return, the Dark Presence would give him back Barbara. Zane complied and began writing the story.
But when the Dark Presence returned Barbara to Zane, she was changed and not the same anymore. Terrified, and realizing what the Dark Presence was trying to do (get enough power to destroy Bright Falls), he cut out the new Barbara's heart with a knife. Zane, who was an avid diver, donned a large diving suit and dived into the lake with the new Barbara, where he drowned.