Which 3rd party D&D book introduced new rituals that gave player characters monstrous body parts and their associated powers?

Question

A long time ago, I remember reading a book which introduced new spells that allowed a player to take abilities from monsters by performing ritual magic that gave them the body parts associated with those powers.

I do not remember the name of the book but I do remember that there was a flavor text excerpt where someone attempted to gain the lungs of a gorgon so they could use its petrifying breath weapon. The person either died from asphyxia during the ritual due to losing their lungs during the ritual before getting the monster organ or woke up from passing out with a metal bull head.

In another excerpt I remembered an evil wizard's apprentice finds that his master was killed by the rat headed human bodied soldier creation that he was experimentally creating using the magic from the book.

I vaguely have the idea that this book was part of a series detailing 3rd party variant "spell schools" but I do not remember what the topics of any others in the series would have been so I may be mixing this up with a different book.

Does anyone know the name of this book or who published it?

Answer 1

Crossbreeding

While published much earlier than remembered, Jonathan Richards's Crossbreeding: Flesh and Blood (2003), part of Mongoose Publishing's Encyclopedia Arcane line for Dungeons & Dragons, Third Edition, contains a piece of fiction describing Sasha the magician who, after she'd "studied the gorgon's lung structure for weeks," performs a ritual that she hopes will grant her the creature's breath weapon.

To spare those readers sensitive to body horror imagery—but to provide the asker with information that may jog a memory—, I've spoilered the results of Sasha's endeavors below:

Later, Sasha woke up, disoriented. It took her a few moments to remember what happened and then it all came to her in a rush. She sat up in the central circle and looked around, feeling weak. It was an effort even to hold her head upright. She looked around for the body of the gorgon but it was gone, apparently dissipated by the eldritch energies that powered the transmutation ritual. The ritual had succeeded! She gave a cry of triumph, but it came out only as a low moan. Startled, Sasha raised her hand to her mouth—and became painfully aware of her black-plated muzzle. The thick plates covered her head, neck and the space between her breasts. Looking down, the weight of her heavy horns tipped her head violently forward, cracking the back of her neck painfully. Sasha tried to scream in horror but her vocal cords were no longer human, and the bellow that reverberated back and forth in the laboratory sounded strange to her bovine ears. (33)

Crossbreeding also contains the fiction about the rat (3).

Crossbreeding doesn't really contain any spells, but it includes a variety of rituals that can be used to create hybrids of creatures, and, obviously, it includes rules for a creature to use such rituals to hybridize herself.

Answer 2

The Fleshwarper prestige class, from Lords of Madness

This may or may not be exactly what you remember, as it's not 3rd party, but it could very well be the inspiration for what you read or at least something similar enough to meet your needs!

Introduced in the 3.5 Lords of Madness supplement, the Fleshwarper prestige class is almost exactly what you are describing. It has rules for grafting on additional body parts (both humanoid and monstrous) and gaining abilities from them.

The Fleshwarper Class Flavor Text: Lords of Madness page 189

The flesh is the key. It holds the secrets, the hidden words. It is constant between man and beast and monster. It is a simple matter, once the way of the flesh is understood and embraced, to use it to your will.

There have also been some attempts by 3rd parties to convert this class to 5th edition; perhaps one of those is what you are thinking of:

1. https://www.dndbeyond.com/subclasses/117991-fleshwarper
2. https://www.dmsguild.com/product/266512/The-Fleshwarpers