Glow (formerly Radiant) is a spell exclusive to the original Dragon Quest and its remakes.
Glow lights up dark caves by a 4 x 4 radius for 128 steps. Initially, the light is brighter than that provided by a torch. However, unlike the torch, its light eventually fades, leaving the dungeon dark until it is recast. MP required s 3 in the original, and 2 in all remakes.
Since dungeons can be seen without assistance in all other games, this spell does not appear in any other game.