Elder hatefiend

The Elder Hatefiend is a level 234 monster that can be found wandering Runescape.

It will only be hostile to players over level 80, but it may attack any sort of non-quest related NPC, one shotting them with a nameless technique that shows no damage, but kills the NPC. It has a tendency to attack cities, although it rarely gets further than the city gates before a swarm of players forces it to teleport to a different server. It is known to cause temporary environmental damage, such as tearing down the walls of Falador to gain access.

Jagex has not released any information on the creature, except that it is expected to gain an increase in power soon.

First sightings were reported on 15th September 2010, it seems to stay on only one realm at a time, jumping randomly with an in-game animation of spellcasting, and it will always do this when under 500 health. However, it will not appear on non-member worlds.

It is also the largest creature in the game, being some ten squares across, and is unable to cross the wilderness border.

Trivia
Popular speculation is that it is a test for implementing environmental damage into Runescape, largely because of its environmentally damaging attacks and its examine text.