Vestigality

The spellcaster shifts a harmful amount of unstable life energy into another creature, resulting in a disgusting, if temporary, transformation. 

Target an organic creature with this spell so long as you can make skin contact with their skin, fur, feathers, or hide.  The creature must make a constitution saving throw.  If the creature fails, they take 1d6 necrotic damage and their body painfully twists and morphs.  Roll a D6 and consult the following table for the effect, which last for 1 minute:

1. Twisted Leg: Growing from inside another leg, this worthless leg with a few extra joints obstructs the functional ones and halves the creature's movement.
2. Shriveled Arms: A few small and motionless arms sprout from exposed portions of the creature, all of which appear malnourished and stuck in different positions.  With these in the way, the creature must make melee and ranged attacks at a disadvantage.
3. Hypersensitive Ears: A number of ears rise from the creature's flesh, making it hypersensitive to noise.  When the creature can hear any noise over the sound level of a whisper for longer than six seconds or a full combat round, it takes 6 thunder damage.  In addition, all other thunder damage it takes is doubled.
4. Rolls of Skin: The creature gains nearly double its normal amount of skin or hide, which rolls through any gaps or openings.  The creature loses 2 AC, has disadvantage on dexterity saving throws, and loses 10 feet of moment, to a minimum of 10.
5. Blighted Wing: An oversized lump of flesh and bones burst from the target's back from wherever there is an opening, then unfurls itself as a single, twisted wing that inherits its appearance from the creature.  If the creature does not have wings, all attacks against them have advantage.  If the creature already has wings, they can no longer fly in addition to the previous effect.
6. Malformed Head: A new head sprouts from one side of the creature's collar.  The head appears similar to the affected creature, but its facial features are twisted to different proportions.  Once formed, it stares at them and screams with only short breaths for break in between.  The creature has disadvantage on all saving throws.

Each spell slot level over the 2nd that this spell is cast, it deals 1d6 more necrotic damage.  This spell can be cast on the same creature even before the previous effect has worn off.  Rolling the same effect adds another minute to the duration.

After the spell's effects end, the extra limb(s) harmlessly falls off the affected creature and it withers to a small, dry husk that cracks apart to dust if handled or exposed to a light breeze.  Constructs are immune this spell and its effects.