Potion of Holding Darkness

This small vial has a single dose of a black poison inside. When ingested, the creature takes 5d6 psychic damage. While the poison
is in effect, the creature is unable to sleep.
When an affected creature attempts to rest, their dreams are plagued by nightmares and
are unable to gain the benefits of a short or
long rest. Only a greater restoration, heal or
wish spell can end the effect.