Curse of Cocytus (3.5e Feat)
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Curse of Cocytus [Epic, Frost Knight]
Your body has frozen to such an extent that it is impossible for disease-carrying organisms to survive in you or for all but the most virulent poisons to affect you.
Benefit: You now immune to all nonmagical diseases, as well as all poisons that have a Fortitude save DC of 25 or less.