Bestow Witch's Curse

You touch a creature, and that creature must succeed on a Wisdom saving throw or become cursed for the duration of the spell. When you cast this spell, choose the nature of the curse from the following options:

• Change the morphology of the head, upper limbs or lower limbs to mix with that of an animal or creature that exist in the nearby area (100ft): (This will impose a Disadvantage on CHA Persuasion checks unless the body part is hidden. The mix will keep the proportions normal for the target's size. Weather or not the target can still hold objects, and any other negative or positive attributes is up to the DM to decide. However the target always preserves all 5 senses, even if the way to perceive them changes (seeing with sonar, etc...)).
  • Chicken Arms with feathers: Can use an action to levitate. Vulnerability to fire damage. Disadvantage on Persuasion checks.
  • Legs of an horse: Speed increase by 10ft. Must roll DEX saving throw if they which to move, to not fall prone. Disadvantage on Persuasion checks.
  • Head of a frog: Grapple up to 10ft with their tongue. Disadvantage on Persuasion checks.
  • Etc...

• Change the physiology of a target's body:
  • Salivary glands under their jaw to enlarge greatly and to produce venomous saliva in abundance that can be spit forward in a 10ft cone. The target must roll a CON saving throw at the end of every turn until the curse is removed to not suffer 1d6 poison damage. 
  • Sweat glands to overproduce, giving the target resistance to fire damage and vulnerability to cold and lighting damage. The target must roll a DEX saving throw to not slip and fall prone due to the sweat that accumulates on the ground where it stands.
• Change the morphology of the body of the target to mix with an element:
  • Turning their skin to stone, giving the target resistance to all non-magical physical attacks but also immobile from the weight.
  • Turning their body into slime, giving advantage against bludgeoning and crushing from objects and falling, but reducing their strength to 1.
  • Turning their body into burning embers, granting them 1d4 fire damage to melee attack rolls and light production of 10ft radius, but reducing their max HP by 1d6 each turn.
  • Turning their skin into that of a wind elemental's, allowing them to levitate and fly, but the altitude changes every turn by d20 ft that must be rolled.
• Heightening a target's sense into overdrive:
  • Vision: The target gets advantage on Perception rolls based on sight, DEX saving throws, and can see clearly any action up to 2000ft. However they must roll a CON saving throw at the start of each turn for an hour, (and afterwards  twice per day if and during any stressful situations like combat for a year) to not be struck by hallucinations that make the target, on their turn, move in a random direction (d8) and take a random action determined by the DM that does not cause self harm.
  • Smell: The target gets advantage on Perception rolls based on smell and Survival rolls for tracking creatures if they were 100ft near him at one point. However they must roll a CON saving throw at the start of each turn for an hour, (and afterwards twice per day if and during any stressful situations like combat for a year) to not be struck by hallucinations that make the target, on their turn, move in a random direction (d8) and take a random action determined by the DM that does not cause self harm.
  • Touch: The target gets advantage on all weapon attacks, +2 AC. However they must roll a CON saving throw at the start of each turn for an hour, (and afterwards twice per day if and during any stressful situations like combat for a year) to not have a muscle spasm that forces them prone and immobile for the duration of their turn.
  • Hearing: The target gets advantage on Perception rolls based on hearing, DEX saving throws, and can hear clearly any creature that makes sound up to 500ft. However they must roll a CON saving throw at the start of each turn for an hour, (and afterwards twice per day if and during any stressful situations like combat for a year) to not suffer from extreme pain in their inner ear causing 1d4 force damage.

A remove curse spell ends this effect or the special curse breakers for each curse:

• Body morphology mix: Someone within 15ft of the affected target must cuts the head, upper limbs, or lower limbs of an animal of the same species as the mix.
• Salivary glands: Cut under the jaw of the affected target. 
• Sweat glands: Coating the skin with dirt.
• Skin to stone: Falling 30ft or 20 Bludgeoning damage to the affected target.
• Body to slime: Immersion in fire or 20 Fire damage to target.
• Body to embers: Immersion in water or 20 Cold damage to the affected target.
• Skin to air: Immersion in dirt or 20 Lighting damage to the affected target.
• Vision: Blindfold temporarily stops the curse (and benefits) or cutting off affected target's seeing organs for permeance.
• Smell: Plugging nose temporarily stops the curse (and benefits) or cutting off affected target's smelling organs for permeance.
• Touch: Immersing hands non running water temporarily stops the curse (and benefits) or cutting off affected target's hands for permeance.
• Hearing: Plugging ears temporarily stops the curse (and benefits) or cutting off affected target's hearing organs for permeance.

One creature can suffer up to 4 curses before becoming unconscious. At the DM's option, you may choose an alternative curse effect, but it should be no more powerful than those described above. The DM has final say on such a curse's effect.

(Inspired by MonsterGarden on YT.)