Magedoom

In a certain tyrant-ruled fortress-city, the resident wizards treat every outside mage as a rival, and the city teems with both. Its mightiest wizards pooled their power to secure their dominance and devised a horror to find and kill foreign spellcasters: the magedoom.

It is a tall cone of wet, glistening yellow-brown sludge, topped by a shriveled, eyeless human head, with two heavy limbs drooping from near the summit. It reeks of ozone, like a lightning strike in the rain, mixed with a sour citrus bite. One doomed mage likened it to being mugged by a rotten, electrified grapefruit.

The magedoom clubs with both limbs for 3d8 each, always choosing wizards first, then priests, then anyone else. Any wizard spell cast inside 180 feet draws its attention: it fixes on the caster and follows. Once in reach, a slick tentacle bearing a shriveled, bloodshot eyeball bursts from its body and, with a successful attack roll, touches the wizard's brow. Each hit drains one level of spellcasting only: an 11th-level wizard now casts as 10th, and any spells beyond the new level vanish from memory. Survivors regain one casting level per hour but must relearn lost spells. Saving throws, THAC0 and hit points are unaffected.

Being blind, it tracks by an unerring sense for magic and by tiny sensors in the slime coating its body and limbs, so it ignores illusions and spells that depend on the target's sight. It also projects a 3-foot-radius anti-magic shell; a fighter in magical armor with a flametongue meets it with mundane mail and an ordinary long sword, though the items work again once outside the field.

When slain, its stored magic erupts in a wave of wild magic. For five rounds, everyone within 15 feet (other than the magedoom) is treated as a wild mage who has triggered a wild surge, with a new surge result rolled each round for each being, who counts as the caster; nonsensical results simply do nothing. Alternatively, treat each being in the area as the target of one wand of wonder discharge per round for five rounds.

A magedoom is made from a living wizard whose body and soul are reshaped by a rare, forbidden spell. The archmage who cast it holds partial control, assigning tasks while the creature decides how to carry them out. If that archmage dies, the magedoom goes rogue and no wizard anywhere is safe.

They are loners. Rumor holds that if two magedooms come closer than 10 feet, a resonance builds that detonates in 1d4 rounds, destroying both and and leaving dead magic across a 40-foot radius for a month, with a 1% chance of producing a sphere of annihilation instead.

Magedooms exist only to murder spellcasters from outside their makers' city. The goddess of magic, the god of wizards and both their clergies despise them, and senior priests sometimes lay a geas or quest to destroy one on those who have wronged their faith. Devoted high-level specialty priests of the god of wizards reportedly gain a unique spell able to unmake a magedoom.