Poison chalice

The poison chalice is a green, sickly-looking beverage given out by the dwarf Stankers, found at the Coal Trucks.

The poison chalice features in the Seers' Village Tasks, in which players complete an easy task by giving one to King Arthur.

The chalice can be drunk by players. Its effects are random, but include:
 * Temporarily boost Crafting, Fletching, or Thieving by 1 level.
 * Temporarily boost combat ability (Attack, Strength, and Defence) by 4 or reduce it by 3.
 * Heal or damage the player: healing players up to 490 life points or damaging them from 30 to 600.

Damage seems to be based on a percentage of the player's life points, at two levels: 5% damage and 60%. It also seems that player with a high amount of life points have lower chances of being damaged by drinking from the poison chalice.

This could be used similarly to nitroglycerin. It can be a potent item for those who use Dharok's set as it damages a lot (up to 600), but it is very risky as it may heal or lose too many life points. After an update the killing effect of this potion was removed, your health will not fall below 25.

Effects
Stankers hands you a glass of strangely coloured liquid...
 * You drink the strange green liquid.

Trivia

 * Despite it saying "Poison", it doesn't actually poison players.
 * The Seers' Village Easy Task is called 'Le Mort d'Arthur' after the classic by Sir Thomas Mallory. It is also the title of an episode of the BBC series Merlin.