Slayer masks are Slayer equipment that can be won from Treasure Hunter and they can also be bought from the Shattered Worlds reward shop. They were released in multiple waves. The first set allows a player to force a slayer task of that creature daily, and the second every 3 days. Using "Check Kills" on all masks/helms with 3 day cool downs will display time left till the task can be forced again.
They provide several bonuses for players looking to train their Slayer skill, including bonus XP, extra damage, and double drops every 10th kill. The mask will also teleport the player twice a day to the relevant monster area/dungeon.
After a certain number of kills (depending on mask), the mask will become a Helm. The helm has similar benefits, but does not provide bonus XP, extra damage, or double drops.
Every creature killed is tallied while the mask is worn. Each mask has a set amount of kills assigned to it that, once reached, "uses up" the Slayer experience and double drops effects, and turns the mask into a helm. The kill count continues to be tracked beyond this point, up to 999,999 kills.
A right-click option announces total kills of that creature. The announcement of total kills is seen in the chat bar and above your character by those around you. If the helm has yet to be unlocked, there’s also a message to say how many more kills are needed to do so.
After the helm version has been unlocked, the player is free to switch between it and the mask version, as a cosmetic preference only – this does not restore the Slayer experience and double drop effects to the mask.
Spirit of Battle is the only way to reset a helm back to a mask and re-enable the mask's benefits.
If attempting to use a slayer mask for a blocked task, the game will inform you of this and ask you to confirm you want it anyway. However, if you attempt to use the Aquanites slayer mask while Aquanites are toggled off in the slayer master rewards menu, the slayer master will automatically give you a regular task without asking you to confirm you wanted one. This could result in an accidental misuse of the mask.
Slayer masks and helms