The sibriex, the sibriex chain master, the sibriex flesh crafter, and the sibriex spawn appeared in fourth edition in Demonomicon (2010).
Sibriexes belong to the ancient race of demon called obyrith. Being obyriths, sibriexes have monstrous forms, which can drive mad anyone who dares look at them. Sibriexes are among the most ancient and mysterious inhabitant of the Abyss. Sibriexes resemble enormous deformed faces floating in the air, linked to the ground by metal chains.
Sibriexes enjoy modelling flesh. It is whispered that they could have a role in the shaping of the actual forms of the tanar'ri and that, for this reason, they have survived the destruction of the obyrith race. However, the number of these creatures is now very low, accounting about few hundreds of them.
When Tharizdun plunged the Shard of Evil into the heart of the Elemental Chaos, he freed the last of the obyriths from their decaying universe. The most powerful of those creatures became demon lords, even as the lesser members of their kind were absorbed by absolute corruption as the Abyss was born. The demons known as sibriexes were spawned from clans of obyrith slavers, savants, and flesh crafters. They haunt the Abyss and the planes beyond, dedicated only to increasing their own power.:146
Like the obyriths from which they are spawned, sibriexes are creatures of an alien universe. Demonologists argue over what motivates these mad creatures, but the inner workings of the sibriex mind might never be known. Regardless, their chaos manifests as a thirst for the subjugation, transformation, and destruction of all other creatures. The other demons with which the sibriexes are now kin they regard as raw material for their experiments.:146
Hovering over the wasted abyssal landscape, the sibriex chain master appears as an enormous, deformed head that seems to be tethered to the ground by heavy chains. As it approaches, panic sets in among its foes, a nameless revulsion shattering their resolve.:146
As its Sibriex Horror aura spreads debilitating fear among its enemies, a chain master soars across the battlefield, making devastating melee attacks. When a number of its foes are immobilized or knocked prone, the chain master unleashes bile spout to reduce them to pools of acidic gore.:146
The flesh crafter is the artist of demonic forms, employing its flesh-warping disease to corrupt the forms of its foes.:147
The battlefield is the flesh crafter's playground, allowing it to experiment in the creation of new demonic forms. The creature uses its melee and ranged attacks to restrain and expose foes to the flesh warp disease, then unleashes instant warp.:147
The foul nature of the sibriexes can infect other creatures, creating vile spawn beholden to more powerful masters. It is the only one that barely understands Abyssal.:147
These misshapen spawn surge ahead of their more powerful allies in battle. They trust in their aura of fear to sow chaos, waiting for the attack that reduces them to an explosion of deadly bile.:147
The sibriex are arrogant creatures that have no equals among their allies. They are found either as the lords of lower-level thralls, or under the dominion of a powerful demon lord. Even when serving a more powerful master, a sibriex seeks out any opportunity to free itself, growing increasingly ruthless and cruel in the process.:147