The Sixfold Ossuary
The Sixfold Ossuary is a necromantic guardian that protects a sealed passage beneath a flooded cavern. It does not attack immediately. Instead, it studies intruders through the skulls on its pillars, raising drowned dead from the pool and forcing the party to choose between fighting the minions and dismantling the guardian. Each round, the blue flame shifts between pylons, causing one pillar to empower the guardian while another prepares to erupt.
The Sixfold Ossuary
Defenses
Detection
“A ring of six black stone pillars surrounds a waist deep pool of perfectly still water. Each pillar bears a carved skull with silver wire threaded through its teeth. Pale hands occasionally press against the underside of the pool's surface, as though drowned corpses are trying to climb out. A crown of blue corpse-flame burns above the center of the ring without consuming any fuel.”
Standard Engagement
The guardian activates when a living creature enters the ring of six pillars, touches the sealed passage, attempts to take the central corpse-flame, or damages a soul pylon. It remains active until disabled or until no living creature remains in the shrine.
On initiative count 20, the guardian performs one routine, choosing an option based on its remaining active pylons. With six to four active pylons, it uses Soul-Burning Aura and Pylon Discharge, then raises 1d4 drowned skeletons. With three to one active pylons, it uses Soul-Burning Aura and Pylon Discharge, but raises only 1d2 drowned skeletons. If no pylon is active, it cannot perform its routine. The guardian always targets a different active pylon for the discharge each round when possible.
If not permanently disabled, the guardian resets after 10 minutes without a living creature in the shrine. Destroyed drowned skeletons reform from the pool when it resets. Disabled pylons remain disabled until the guardian is repaired or the shrine is restored by necromantic ritual.
Each hostile creature that starts its turn within 20 feet of the central flame must make a DC 16 Constitution saving throw. On a failure, it takes 14 (4d6) necrotic damage and cannot regain hit points until the start of its next turn. On a success, it takes half damage and suffers no healing restriction.
The active pylon releases a lance of blue flame at one creature the guardian can sense within 60 feet. The target must make a DC 17 Dexterity saving throw, taking 22 (4d10) necrotic damage on a failure, or half as much on a success. If the target fails by 5 or more, its speed is halved until the end of its next turn.
The pool produces 1d4 drowned skeletons at unoccupied spaces near the pool's edge. These undead act immediately after the guardian in the initiative order. The guardian can have no more than eight drowned skeletons under its control at once.
The guardian has six soul pylons. Each pylon is an object with AC 17, 25 hit points, immunity to poison and psychic damage, and resistance to nonmagical bludgeoning, piercing, and slashing damage. A disabled pylon cannot be targeted by the guardian's routine.
Whenever a pylon is destroyed rather than disabled, the guardian releases a backlash. Every creature within 10 feet of that pylon must succeed on a DC 16 Dexterity saving throw or take 10 (3d6) necrotic damage and be pushed 5 feet away.
The guardian can sense living creatures and undead within the cavern, even through darkness, water, or thin stone. It cannot sense creatures protected by a spell such as nondetection unless those creatures deal damage or activate a magical effect inside the shrine.
Radiant damage dealt to the central corpse-flame counts as double for the purpose of reducing its hit points. Necrotic damage dealt to the flame restores an equal number of hit points instead.
When the corpse-flame is reduced to 60 hit points or fewer, all remaining pylons flare. Until the guardian is disabled, the Soul-Burning Aura deals 21 (6d6) necrotic damage instead of 14 (4d6).
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