Delrith

Delrith is the demon summoned to destroy Varrock originating from Infernus. In the past, he was banished by a miner, Wally, and when a gang of cultists led by Denath summons him again in 169, an adventurer dispatches him with the aid of Gideon Bede, a Saradominist scholar.

He has a combat level of 15 (60 in Dominion Tower) and appears in the crypts below the Zamorakian church in the Demon Slayer quest. He is fight-able as a class H boss monster in the Dominion Tower minigame if the player has completed Demon Slayer. A copy of Silverlight is provided within the arena.

In battle
In battle Delrith uses Melee and Magic. His most powerful attack is a spell he uses to try to incinerate his opponents. If not defended against using Gideon Bede's barrier, it will reduce your life points to 1 regardless of your current life point total. Even with protection, it will still cause nearly 20% damage to your current life point total.

The demon can only be attacked with Silverlight, a weapon enchanted by Guthix to maintain the balance of Gielinor, and no other weapon or the message "I'd better wield Silverlight first" appears.

History
It is implied by the Demon Butler that Delrith originated from Infernus as a Demon Lord whom he served under, and in Demon Slayer.

Many years ago, the druids of Taverley had many stone circles built across Gielinor. At these sacred altars the druids would worship Guthix, the god that shaped, but not created the planet. One such circle was found just outside of Varrock, the massive capital of Misthalin. For some years it stood as a beacon to the followers of Guthix.

The circle was destined to fall, however. 150 years ago, in the year 19 of the Fifth Age, the stone circle was captured by an order of dark wizards, who, for unknown reasons, sought to destroy Varrock in Zamorak's name. It was here that they summoned Delrith although he was swiftly defeated by Wally.

Demon Slayer
During Demon Slayer, a cult of cultists and a man named Denath prepare to summon Delrith once more in the Church of Zamorak in the southeast of Varrock by stealing a tome from the monastery near Edgeville. Gideon Bede, who had been in charge of the Monastery's library, followed Denath to Varrock where he recruits an adventurer to aid him. Once the adventurer accepts the offer to help, they begin Demon Slayer.

To defeat Delrith, the adventurer must acquire Silverlight, while Gideon tracks down Denath. After dispatching Denath's followers, Gideon and the adventurer reach Denath who manages to summon Delrith. Between the adventurer's attacks wielding Silverlight and Gideon's massive protection prayer, they manage to defeat Delrith once and for all. Once Delrith is defeated, the cave under the Zamorakian church collapses, but Gideon and the adventurer manage to escape.

Dimension of Disaster
In Dimension of Disaster, Delrith was successfully summoned and went on a rampage through Varrock, killing many people including Gertrude's sons Wilough and Shilop. He enjoyed terrorizing the people of Varrock until Zemouregal and his zombies invaded, and seeing how destructive and perhaps annoying he could be, Zemouregal threw him in the southeastern area of Varrock. To make matters worse for Delrith, the demon Agrith Naar began bullying him from Infernus, and he longed to return to his home realm.

The adventurer shows up and Delrith believes that they are just another "crazy cultist". After they use Silverlight on him, he realises that he has a chance to escape and enlists them to get him out of New Varrock. The adventurer gets a vial of blood, and Delrith guides them through the process of making a blood circle. The adventurer later stabs him while he mutters the incantation to return to Infernus, and upon returning back in his home world, banishes Agrith Naar to New Varrock.

Trivia

 * In the 3rd Postbag from The Hedge, one player asked about Delrith being "naked" and he responded that he is embarrassed about being naked and immediately sends out one of his wizards out to get new clothes for him. And that when he sees his reflection in the blade of Silverlight his combat level drops down to 27 because of his embarrassment. This, of course, is just a joke and shouldn't be taken too seriously.
 * Delrith was the first strongest quest monster fought in RuneScape. Later, when the Vampire Slayer quest was released, the Vampire, Count Draynor, succeeded him as the strongest quest monster.


 * Interestingly, he used to have have less health than a level 3 player just starting to play, and even Imps had more health than him, This is due to the fact that he has been freshly summoned and, as a result, still weak from his movement between dimensions.