Core Spawn Worm

Habitat Underdark

The Elder Evils assault the multiverse in strange and calamitous ways. Sometimes they breach the Material Plane by exploiting the unfathomable energy and darkness found in the world's depths. These terrestrial manifestations of loathsome alien agendas are known as core spawn, and they are as varied in their physiology as they are horrific.
Their concentration in the desolate lands of Blightshore makes the core spawn a challenge to research, and many who have sought to observe or study these nightmarish entities rarely return. Those who do return are often shells of their former selves who speak of horrifying underground labyrinths of twisting caverns and malevolent nests where other denizens of the Miskath Strand are dragged below to some infernal purpose.
Offspring of Calamity. The aberrant creatures known as core spawn are a subterranean breed of heralds, servants, foot soldiers, and lieutenants of the Elder Evils, awakened in the depths by the cataclysmic actions of the Betrayer Gods and their minions. They often appear on the surface world in the wake of seismic events, such as that which created the bottomless Miskath Pit of Eastern Wynandir. Warlocks and cultists sometimes gather together to hasten the arrival of core spawn to the Material Plane, focusing their arcane power on areas of natural seismic instability when the signs and stars are right.

This invertebrate horror has quivering, barbed tentacles set around its massive, toothy maw. The worm's cracked and stony hide pulses with a dull orange glow, as if it might be composed of primordial lava perpetually on the verge of hardening into solid rock.