Needs review
Source: Dragon Magazine #343

Description: You have taken a vile green Kyuss worm into your own body and bound yourself to its power.

Prerequisites: Living Creature, Host a Kyuss Worm

Successfully hosting a Kyuss worm requires a special binding ritual. The ritual requires 4 hours of uninterrupted meditation, 500 gp in special materials, and a living Kyuss worm. At the end of the ceremony, you must succeed at a DC 15 Fortitude saving throw or die. If you fail the saving throw, you rise as a spawn of Kyuss within 1d6+4 rounds. If you succeed at the saving throw, you can add the following spells to your class spell list:

2nd - path of worms

3rd - consume the parasite, the worm within

4th - mindworms

5th - servant of the green corruption

7th - extrude wormswarm

You must still learn and prepare these spells according to the normal spellcasting rules for your class. The worm can be removed only by casting one of the following spells: dispel evil, heal, remove curse, or remove disease in a hallowed area, or by casting consume the parasite. If the worm is removed, you cannot cast these spells and lose any of these spells that you may have prepared. You must repeat the binding ritual to regain this feat's benefits.

Special

If you die with a living Kyuss worm inside you, you rise as a spawn of Kyuss within 1d6+4 rounds. As a spawn of Kyuss, you exist only to spread the corrupting power of Kyuss and have no free will of your own (meaning that the spawn of Kyuss becomes a monster under the DM's control).