The Helm is obtained after killing a number monsters while wearing the relevant mask. The helm has similar benefits to the mask, but does not provide bonus XP, extra damage, or double drops.
It does allow a slayer to force the choice of slayer task to this monster (daily or every 3 days depending on monster). It does provide free teleports to that monster (most provide 2 teleports daily).
The mask's kill count carries over to the helm and continues to be tracked, up to 999,999 kills.
A right-click option announces total kills of that creature. The announcement of total kills is not seen in the chat bar but is seen above your character by those around you.
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.
After the helm version has been unlocked, the player also unlocks an emote in which they can transform into its monster for few seconds.
Slayer masks and helms