A Helghast is a powerful, skeletal shape-shifting monster from Helgedad. The word is both singular and plural.
In its true form, a Helghast looks like an undead creature with a rotting face and glowing red eyes, and it nearly always wears a long hooded cloak. Helghast can disguise themselves as humans and other creatures and are thus often used as spies and assassins. They are very strong and are immune to ordinary weapons. They can only be damaged by magic weapons (such as the Magic Spear), and because Helghast are undead, the Sommerswerd is doubly damaging to them. Helghasts played a critical part in the Darklord campaign against Sommerlund during the Helghast Wars. Upon their destruction, they turn into a vile green gas. They always use Mindblast in combat; those without Mindshield will steadily lose Endurance Points during battle. Stronger Helghast can use Psi-Surge and will quickly overwhelm those without Psi-Screen, rendering Mindshield useless. They're also immune to Mindblast.
The Gnaag Helghast encountered here has the nasty ability to drain 2 Endurance Points per round unless Lone Wolf possesses Psi-Screen. This is written to be a cumulative loss until the Helghast is defeated.