Darklight

Darklight is a magical sword obtained in the Shadow of the Storm quest. Silverlight becomes Darklight after destroying the demon Agrith-Naar and being coated in ichor (demonic blood). Both Silverlight and Darklight can be mounted on the wall inside of a player's home if he or she has a Quest Hall. This weapon cannot be made using the Smithing skill.

While fighting Lesser, Greater, Black or Abyssal Demons, the maximum hit a player can normally hit is increased by a fair amount, approximately the same strength as a dragon longsword. Its accuracy doesn't increase though, so you can still likely miss.

Note: If you die and lose Darklight, you can go back to Varrock Castle and talk to Sir Prysin to pay 1000 coins to get it back. A player may have multiple Darklights by the same method used to attain multiple Silverlights.

Darklight has a special attack, Weaken, which lowers the opponent's Strength, Attack and Defence levels by 5% (10% for demons).