Sounds like a Gauntlet/Diablo style game.

The light feature could be a good idea though, there was a game back in the day called Cadaver, it was on the Amiga.. an Isometric 3D dungeon game where you cast light and it affected the dungeon.. I think there were light based puzzles.. different coloured light activated different switches.. That would add a puzzle element to the dungeon crawler RPG genre.

If you're making light a feature, you could have different types of light affecting the creatures too.. some creatures are repelled by different types of light, others are destroyed by types of light, some are attracted by certain types yet destroyed by others. Think "Pitch Black" the movie...

Not afraid of the Dark are you?