From publisher blurb:
Chaos Works Upon The Flesh is a survival horror supplement for 5e and 5.5e that will add the power of the Shapeless to your game, a chaos entity of twisting flesh and mutant growths.
Horrors lurk under the surface, new Shapeless monsters like Croneys, short for Cronenberg monsters, deformed humans growing eyestalks out of their backs or whose fists have fused into clublike slabs of callouses and bones, or conglomerates, chimeras, and shoggoths, who have unstable anatomies formed of several different creatures melded together, or blood horrors, creatures of animate blood and gristle caused by uncontrolled healing power that animates a pile of indistinct viscera. Familiar monsters have been tied to the dark power of the Shapeless, like trolls whose regenerative cannibalism is right at home with the supernatural cancer, and who grow steadily larger until they eat so much that their bones break under their own weight and a horde of goblins sloughs off the broken mass.
The Ether Knight is a level 1-20 base class with three sub-classes, an occult warrior whose magical powers are fueled by ether, the substance of both the Shapeless and other distortion entities like it. The Ether Knight's powers are intimately tied to the horrors of chaos. Focused on tanking and support, the Ether Knight wields the powers of Shapeless ether to stitch the bodies of themselves and their party members back together from horrible wounds, but beware, overhealing with the power of the Shapeless can cause random mutations which might be anything from changing the color of your eyes to withering away an entire limb to being instantly killed in a sudden explosion of cancerous flesh.
Use the power of the Shapeless to twist flesh back together or to warp the flesh of yourself or your allies, from straightforwardly enhancing the liver to give yourself poison resistance to regenerative cannibalism to the wiring of the spinal tissue to the stomach to allow for mnemophagery - the devouring of memories - to the growth of a crystalline tritosphere in the brain to allow you to survive past death. Immortality doesn't generally go well in horror but the alternative is death, pick your poison.
And make full use of 5e's survival horror DNA held over from earlier editions. Modern D&D focuses on heroic fantasy, a superhero story where the supervillain is a wizard or a dragon, but the old survival horror mechanics are still there, lurking in the subconscious of the system like a nightmare. With the right adventure structure, these vestigial elements can be used to run a survival horror game without any additional mechanics. We do also have some additional mechanics, horror healing potions with unpredictable effects and a revised injury table with more permanent side effects, but the core mechanics of survival horror were always there, waiting to be exhumed.