A to Z: Brimstone monolith

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Brimstone Monolith
Available to: Magic-users (elementalists & diabolists)
Level: 9
Duration: 4d6 rounds
Range: 30'

This powerful and dangerous spell creates a short-lived dimensional rift, summoning forth the destructive powers of other planes of reality. Two different versions of this spell are known to exist, one used by elementalists and one used by diabolists. The elemental version opens a gateway to the elemental planes of fire and magma, while the diabolic version opens a gateway to hell.

The incantations required to complete this spell are more complex than usual, and require several rounds to cast. Each round of the casting a different effect occurs, as follows.

1st round: An earthquake occurs, as the 7th level cleric spell, centered on the caster.
2nd round: A monolith of brimstone rips through the fractured surface of the earth within range of the caster. The monolith is approximately 20' high and 10' in diameter. All creatures within 60' of the monolith, including the caster, but excluding those with immunity to fire, suffer 2d6 hit points damage per round due to the searing heat and flames which surround it.
3rd round: Upon the final round of the incantation, the dimensional gateway is opened, summoning forth creatures from the connected plane (see table below). The summoned creatures are not under the caster's control, and are bent on causing as much destruction as possible.

If the casting of the spell is interrupted in any way, the effects described for any subsequent rounds do not occur.

Once the spell is complete, the monolith begins to shudder, emitting a deafening roar, and shooting out jets of magma and sheets of flame. Every round after the third there is a 1 in 4 chance of a randomly chosen target within 100' being hit by one of the monolith's emissions, causing 5d6 damage (save versus wands for half damage).

To determine which creatures pass through the dimensional rift, roll 2d6:

2: Imix, prince of evil fire creatures (AD&D Fiend Folio) / the arch-devil Bael.
3 - 5: An efreeti and 1d4 8HD lava or fire elementals / a pit fiend and 1d4 barbed devils.
6 - 8: 1d4 12HD lava, fire or earth elementals / 1d4 horned devils.
9 - 11: 1d4 flame salamanders / 1d4 bone devils.
12: A flame salamander, an efreeti and 1d4 8HD lava or fire elementals / a pit fiend, 1d4 horned devils and 1d4 barbed devils.

The gateway allows travel both ways between the connected planes, thus it can be used (presumably in unusual circumstances) as a means of gaining entry into hell or the planes of fire and magma.

When the spell's duration comes to an end, the monolith recedes into the earth, all summoned creatures disappear, and the dimensional rift closes.

In addition to the dangers inherent in casting this spell, there is a 20% chance that the caster gains the attention of either Imix or Bael. The attention of these beings is seldom sympathetic.