Delrith

Delrith is a level 30 demon and the main focus of the Demon Slayer quest. He resides in the stone circle south of Varrock and, despite his appearance, will not attack nearby players.

Demon Slayer quest
During the quest, the player must kill Delrith using the legendary sword Silverlight. Despite his high combat level, he is weakened substantially by the sword, and has a low max hit of 3. This quest is relatively easy to complete even with low-level combat skills.

Overview
Silverlight was a powerful sword used to defeat Delrith 150 years age by the hero Wally. In order to strike the final blow to Delrith, the player must recite an incantation (Carlem Aber Carmerinthium Purchai Gabindo) to seal Delrith inside the dolmen of the stone circle. The only reason that Delrith is such a low-level for a demon is because he is freshly summoned. He is regaining his energy slowly and is still weak from traveling between dimensions.

Strategy
Wielding Silverlight with the first hit struck will greatly weaken the demon. Low-level players should charge straight at Delrith and try to avoid the more dangerous darkwizards wandering around him. When the demon is weakened, a dialogue will appear and prompt the player to select the correct incantation.

Finishing up
Once Delrith is defeated, the Demon Slayer quest is instantly completed, and the player receives the rewards, including 3 Quest Points.

Other notes

 * It is possible to fight Delrith for extended periods of time. Eventually the player will kill Delrith and he will despawn, even if an incantation is not said, however this will not trigger the end of the quest, and he will respawn again
 * It is possible to switch weapons on Delrith after the dialogue choices for incantations appear, however this results in the player being unable to complete the quest until they attack the demon again

Post-quest

 * Delrith will respawn like any other monster
 * Attempting to attack Delrith post-quest results in the following message: