a sombre bottle

This bottle is made of dark, stained glass which upon closer inspection yields an almost smokey complexion. A simple cork stopper plugs the mouth of the bottle. The shape is quite unnatural; no sides are the same, and it is even only on its bottom.

It is a sombre bottle.
It weighs half a pound.

You identify a sombre bottle.
It is a potion.
It decreases willpower by one and perception by three for ten hours.
After that, it increases defensive bonus by two and decreases perception by two for sixty hours.
After that, it increases defensive bonus by one and decreases perception by one for thirty hours.
It weighs seven ounces, and it is worth about ten celeb.
Its keywords are bottle, sombre, and potion.