Pyroclasm (3.5e Spell)

Flame and ash leave none behind, from either nature or mankind.

While casting this spell, you draw vast amounts of matter and energy from the interstice between the elemental planes of Earth and Fire and the energy plane of Negativity, and compress it into a bright-white, swirling orb of conflagrant ash 1 foot across, which you then lob at the intended target area. On mental command, the orb explodes into an expanding front of roiling ash and flame that fills up all open space within a radius of 60 feet, up to a height of 30 feet from the ground. Every creature and object caught within the area of the pyroclasm take 1d6 points of damage per caster level. Combustible objects like those fashioned from wood, straw or other crude building materials take double damage. Noncombustible objects dampen the effective damage of the pyroclasm by an amount equal to their hardness. Evasion and improved evasion cannot reduce the damage below one half, even on a successful save.

The flames and ash from the pyroclasm continue to propagate, spreading through tunnels, cracks and openings, expanding around and flowing fluidly between obstructions and buildings that are scored and left to burn and crumble in its wake. Every subsequent round during your turn, the conflagration expands through all open space within 60 feet of the area currently occupied by the pyroclasm, adding that space to its area, but the damage of the pyroclasm is reduced by one damage die every round. The burning ash keeps propagating, slowly cooling off until the spell runs out of damage dice, at which points the pyroclasm stops expanding and no longer deals damage. A sufficiently large body of water or a water spell of 8th level or higher can stop the pyroclasm in its tracks, preventing it from expanding into the area of that spell's effect.

Within the the pyroclasm, all oxygen is rapidly consumed, rendering everyone in the area susceptible to the dangers of suffocation. Any creature not immune to fire will find it impossible to hold their breath due to the intense pain, and must start making Constitution checks immediately, but creatures immune to fire can hold their breath normally. In shielded areas or underground passages where the pyroclasm propagated, the air remains starved of oxygen for up to 10 minutes after the spell ends.