if I remember correctly, you can get source of light by either talking to Othra about making the glowing amulet (after harvesting glowshroom from the cleanse water area) or crafting the torches yourself using workbench or something at your house
You can craft a tourch at home, or get the priest to give you a glowing necklace, if you bring her 5 glow shrooms (I think) make sure you have one or the other equipped
