Ball of Cancer

You hurl a ball of pure, malevolent necrotic energy at a creature. The target must make a Constitution saving throw or become infected with a rapidly mutating Arcane Cancer. This cancer progresses through stages; the target must make a Constitution saving throw at the end of each of their turns, or the cancer advances to the next stage. If the saving throw succeeds, the cancer does not advance.

Stage 1
-1d6 necrotic damage per turn
-Disadvantage on Constitution saving throws

Stage 2
-2d6 necrotic damage per turn
-Disadvantage on Constitution saving throws
-Speed ​​reduced by 10 feet

Stage 3
-3d6 necrotic damage per turn
-Disadvantage on Constitution saving throws and attack rolls
-Cannot regain hit points

Stage 4
-4d6 necrotic damage per turn
-Disadvantage on Constitution saving throws and attack rolls
-Stunned for 1 round

Stage 5
-Instant death
-Boss rule: Bosses do not die. Instead, they take 8d6 necrotic damage and revert to Stage 4 without being Stunned.

Disclaimer: Healing abilities and effects that remove diseases apply to this spell; Lesser Restoration removes one stage of the cancer, and Greater Restoration removes three stages. The spell counts as a curse and can be removed as such. Enemies immune to disease cannot be affected by this spell. Conditions may vary depending on the DM