Ink
This blue-black fluid resembles quill ink but smells like rotted flesh. A drop must be placed on the eye to be used.
Effects.
The user makes a DC 18 Intelligence saving throw or is stunned for 1d6 rounds. If the roll is a 1, the user suffers from increasing madness.
The user’s Constitution ability score is increased by 4 points, for 24 hours.
User’s pupils dilate fully for 24 hours, and they gain Darkvision 120 feet or have their Darkvision increased by that range. The user loses normal vision, can only see in shades of gray, and gains sunlight sensitivity (while in bright light, the user has Disadvantage on attack rolls and checks that rely on sight).
The user gains Advantage on all Constitution saves.
Overdose. If more than one dose is used within 24 hours, the user must make a 22 Constitution save, or become blind as their eyes melt away.
Addiction. DC 12 (Constituion), daily dose. Failure to get a dose - 1d4 reduction to Constitution.