The Helm of Grotesquery is the result of killing 800 Gargoyles with the Mask of Granite, which is won from Treasure Hunter. It requires 45 Defence to wear. As the helm is obtained by killing 800 gargoyles, the minimum slayer level to obtain the helmet is 75 without boosts.
Once per day, while wearing the relevant mask, the next assignment the player receives will be gargoyles. They will still need to go to a Slayer Master that normally assigns these creatures – 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.
Twice per day, this mask will teleport you directly to a choice of locations where gargoyles can be found.
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 outputs total kills of that creature.
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.
After the helm version has been unlocked, the player also unlocks an emote in which they can transform into a gargoyles for few seconds.
The helm's emote previously transforms a player into Sharathteerk, Zemouregal's gargoyle minion, rather than a regular gargoyle. With the graphical update to gargoyles on 29 September2014, the helm's emote now transforms to a regular gargoyle.