The Mask of the Yellow Wyrm is a slayer mask obtained from Treasure Hunter, or from the Shattered Worlds reward shop for 45 million anima. It is associated with the desert strykewyrm slayer monster. It gives two free teleports to the monster per day, as well as extra Slayerexperience while on a Slayer task of this monster and double drops on every tenth kill. The extra experience and drops are lost when the mask reaches a certain kill count, at which point it can be transformed into a helm.
Once every three days, the next assignment the player receives will be desert strykewyrms. They will still need to go to a Slayer Master that normally assigns these creatures (Kuradal or Morvran) – if they do not, the player will be told which Slayer Master assigns them. This does not work if they are in the process of setting up a co-op Slayer assignment. The cooldown is shared across all three wyrm masks. The cool down period of this ability may be checked via the "Check Kills" option on the item's right click menu.
The mask confers the same damage boost against desert strykewyrms (but only while on assignment) as the Slayer helm.
Killing desert strykewyrms while wearing this mask will grant additional Slayer XP equivalent to the Slayer level required to fight them. This is given regardless of the current assignment the player has and in addition to assignment and/or contract XP. The XP awarded by the mask can be boosted by items.
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 XP and double drops effects, and turns the mask into a helm. The kill count continues to be tracked beyond this point, up to 1,048,575 on the item's tooltip. However, only up to 999,999 can be displayed to others with the "check kills" option.
A right-click option outputs total kills of that creature. 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 XP and double drop effects to the mask.