Fire Warrior of Lesarkus

Lesarkus the Fire Warrior is encountered while exploring the Temple of Ikov quest. He guards a door that leads to Winelda the witch. When players attempt to open the door, Lesarkus will appear and demand that they identify themselves. If the player chooses to identify themselves as a humble pilgrim, he will comment that no pilgrims have been to the temple for hundreds of years, and will tell the player that the temple is closed. If the player says instead that they are a mighty hero, he will become enraged and attack. He is level 84, and due to being a creature of pure fire, he can only be defeated with ice arrows that are collected in an earlier part of the temple. He uses fire-based magic attacks. If the player takes too long to kill him, he will simply disappear and the player will have to make him appear again.

Trivia

 * If you try to open the door again before defeating the warrior, you'll summon more of them. Apparently you can do this glitch unlimitedly. Even if log out the Fire warriors will stay on the room. Though, you only have to kill one to continue the quest. This can only be done before killing the first warrior, after which the door can be opened.
 * He used to be known as Lesarkus the Fire Warrior but Jagex changed his name in an hidden update.