Eldritch Rift (3.5e Invocation)
From D&D Wiki
You create a tear in the fabric of space which allows the void to spill into the world. As part of this invocation you designate one 10ft cube/2 caster levels. These cubes need not be touching and can be placed anywhere in close range.
The area under the rift is affected as if by deeper darkness.
Anything that passes through or stops in the sphere takes damage equal to 1d6/2 caster levels (Max 10d6). This damage repeats each round a creature spends in the rift.
Creatures under the rifts when they're opened are allowed a Reflex save to move to the edge of the rifts and take no damage, while creatures voluntarily moving through the rifts are entitled to a Fortitude save for half damage.
This damage is typeless and not subject to energy resistance or spell resistance since it's neither elemental nor magical in nature.