You create a deep pit with a pool of molten lava at the bottom.

LAVA PIT

School conjuration (creation) [fire]; Level sorcerer/wizard 4, summoner 4, antipaladin 4

Casting Time 1 standard action

Components V, S, M (a pinch of volcanic ash), F (Fine shovel worth 10 gp)

Range medium (100 ft. + 10 ft./level)

Effect 10-ft.-by-10-ft. hole, 10 ft. deep/2 levels

Duration 1 round + 1 round/level

Saving Throw Reflex negates; Spell Resistance no

You create a 10-foot-by-10-foot extradimensional hole with a depth of 10 feet per two caster levels (maximum 100 feet) with a 5-foot-deep pool of molten lava at the bottom of the pit. Creatures who fall into the pit take falling damage as normal (the lava counts as a yielding surface), plus 2d6 points of fire damage per round spent in contact with the lava. In addition, exposed items and flammable items carried by a creature in the pit may be be set aflame. You must create the pit on a horizontal surface of sufficient size. Since it extends into another dimension, the pit has no weight and does not otherwise displace the original underlying material. You can create the pit in the deck of a ship as easily as in a dungeon floor or the ground of a forest. Any creature standing in the area where you first conjured the pit must make a Reflex saving throw to jump to safety in the nearest open space. In addition, the edges of the pit are sloped, and any creature ending its turn on a square adjacent to the pit must make a Reflex saving throw with a +2 bonus to avoid falling into it. Creatures subjected to an effect intended to push them into the pit (such as bull rush) do not get a saving throw to avoid falling in if they are affected by the pushing effect.

The walls of the pit are coated with brittle volcanic rock and have a Climb DC of 30. When the duration of the spell ends, creatures within the hole rise up with the bottom of the pit until they are standing on the surface over the course of a single round.