Natharian crystal

Cursed

When in contact with the skin of a creature the crystal starts to adhere to it, you need to use an action do a Strength check (DC 12) for detaching the crystal. When the crystal is detached from somebody, the crystal produces a burst of necrotic energy: both creatures need to do a constitution saving throw (DC12) or take 1d12 necrotic damage (if the same creature is stick and detach the crystal, he does his roll with disadvantage)

The crystal stick in the same way when in a stomach.

If the crystal stays stick for more than 5 minutes he corrupts his host which became corrupted.