Corpselight

This spell causes a body, either dead or undead, to give off a faint green radiance, from a thin nimbus outline to a full torch-like aura. The brightness is adjustable by the caster as long as he is within 30 ft. of the body. The glow spreads out evenly over the corpse and does not flicker. This emanation is not harmful to the undead. While this spell is typically used to create a stationary light source, it can also be used to illuminate invisible undead. It does not prevent the undead from turning invisible, however.

At Higher Levels. If you cast this spell using a spell slot of 2nd level or higher, the duration is concentration, up to 10 minutes. If you use a spell slot of 4th level or higher, the duration is 8 hours. If you use a spell slot of 6th level or higher, the duration is 24 hours. If you use an 8th level spell slot, the spell lasts until it is dispelled. Using a spell slot of 4th level or higher grants a duration that doesn't require concentration.