Generic, Text: Disease: Corruption

Should this initial DC be beaten, the creature no longer suffers any further complication. On a failed save, the corruption will set into the first stage within its new host and either progress or end, depending on the stage its been beaten at.

The disease at this point will cause no further issues in the new host. But at the end of their second long rest after infection, the creature must make another Constitution saving throw, DC 13. Should they succeed, they are able to fight off the incubating disease and are cured of the disease. If the character fails this saving throw, then they enter Stage Two.

Now that the incubation period is complete, the negative effects of the taint have begun to spread through the body. You are to inform the player that their character feels more emotional than normal, more easily angered, depressed, happy, and so forth causing severe mood swings. Their rest will also be hindered with nightmares, causing them to suffer one point of exhaustion after they take a long rest. After they have taken 3 Long Rests in this stage, they must make another Constitution saving throw, DC 15. Should they succeed, they are cured and gain a permanent +2 to their constitution ability score, but it cannot push the stat beyond the base 20 cap. A failed saving throw forces them to enter Stage Three.

Now that the disease has spread throughout your body, you have begun to suffer intense bouts of pain and unnatural bursts of strength and magic normally beyond you that seem to come and go. You suffer the same negatives as Stage Two, along with the following. The critical range of all your attacks are lowered by two (ie. From 20 to 18, or lower for some subclass, etc). After every Long Rest, you must roll a Constitution Saving Throw, DC 11. On a failure, you will gain +2 to a random ability score chosen by your DM (roll a 1d6 and apply a stat to each number for these rolls) and -1 to another. This can never raise a stat beyond the 20 cap, or lower it beyond a base of 6. These are represented as physical mutations, such as tumors, abnormal muscle mass increase, skin discoloration, facial swelling, etc.

After three long rests, your character must make another Consitution Saving Throw, DC 17. With a success, you are considered "Tainted". Your mutations fade, returning your original stats to their normal with this new "feat" for free. A failed save will lead the character's mutations to become permanent. They will adapt to their new situation, they will no longer suffer exhaustion after long rests. But whatever changes to their stats have formed from the mutations are now permanent. The changes can only be cured through a greater restoration spell and a successful cure DC of 20.