In
NetHack, a
potion of full healing will restore 400 hit points. If this would put you above your maximum
hp, it is raised by 4 points. This
potion will also cure
blindess,
sickness, and
hallucination.
A blessed potion of full healing does the same thing, but raises your max by 8, if applicable. Furthermore, if you have been drained of any experience levels (or lost one or more due to divine anger), you will gain one back.
The cursed version simply restores 400 hp, up to your maximum, and will cure blindness and hallucination.
This potion can be quaffed by monsters for similar effects. Inhaling the vapors (if the potion is thrown) will restore up to 3 hit points.
This potion's primary use is to increase one's maximum hit points, as the only other way to increase them is by gaining levels; this is difficult beyond level 14 and impossible after 30. Potions of full healing can be created (a popular activity) by dipping a potion of extra healing into a potion of gain level or a potion of gain energy.