Planar Bestiary
As an undead being, an ossuary blob doesn't require air, food, drink, or sleep; however, they crave flesh all the same.
An ossuary blob is sometimes associated with the Tomb of Winter.
Composed of thousands of skeletal remains of creatures and steeped in the supernatural despair of the Shadowfell, ossuary blobs undergo a transformation from decaying charnel heap to reanimated nightmare when large amounts of necrotic energy are released, which are somewhat rare occurrences even in the Shadowfell. But not rare enough to prevent the creation of these horrific undead.
One might assume by the constant screaming and screeching that an ossuary blob is relatively simple. In fact, the memories of hundreds of dead constituent bodies are remixed in an ossuary blob, creating a new intellect. Though not a pillar of mental stability, an ossuary blob is smart. Moreover, many remember spells that some faction of their constituent remains once knew.
The minds making up an ossuary blob also recall things from long ago that might otherwise be lost to history. Which is why, despite how incredibly dangerous it is, sages and others seeking obscure knowledge sometimes try to parley with these undead. The problem is twofold. One, it's hard to tell when they're lying. Two, they usually try to consume their interlocutors.
The dank charnel odor clogs the air. A clatter of bones accompanies a huge shape rolling into view. It is a rough sphere composed entirely of skulls, spines, bones, teeth, claws, and partial skeletons of all different kinds of creatures. And all of them begin to scream.
Motive: Hungers for flesh
Environment: Necropolises, the Shadowfell, or other places undead shamble
Health: 40
Damage Inflicted: Moderate wound (7 points)
Armor: 2
Movement: Short
Modifications: Speed defense as level 5 due to huge size
Combat: An ossuary blob moves a short distance, making a rollover attack against one or more targets anywhere along their route. Targets that fail a Speed defense task fall prone beneath the ossuary blob as they move over them. Prone victims take damage and must succeed on a Might defense task or be pulled into the blob's interior, engulfed. Engulfed victims automatically take damage each round and all their tasks are hindered. To escape, an engulfed victim must succeed on a Might task, the blob must be destroyed, or the blob must be compelled to expel a victim.
If somehow blocked from rolling over a target, the blob can target a creature within short range with a necrotic pulse, inflicting 7 points of Speed damage (ignores Armor) from necrotic energy.
An ossuary blob is immune to necrotic and poison attacks.
Interaction: Ossuary blobs know all the languages of the corpses making up their form. They can speak in one or many voices and could be negotiated with if promised fresh living victims. However, the blob is a liar, and despite all the knowledge they have accumulated from their victims, feels little desire to share it.
Use: A sage trying to secure important information needs protectors because, as the sage has done before, they wish to again quiz the "God of Formless Despair" that abides in the ruined catacombs nearby.
Loot: The objects caught up in a blob sometimes include valuables, an expensive number of coins (100-200 gold coins), and possibly a few magical cyphers, such as gloves of adhesion and a dagger of banishing.
GM Intrusion: The ossuary blob produces five skeletons from their mass, which do their bidding.