One guiding/description of the Monster Mash says "Monsters chase Warlocks, Warlocks go for Monsters and Shadow Hunters win by hunting them alike."
The Shadow hunter is a hybrid of both, Monster and Warlock. In fact they look really humanoid but have Vampire fangs. That might be a tribute to the Blade films, where the protagonist is a Vampire Hunter although he is a (transformed) Vampire himself.
Tags are important for tiers in the Monster Mash and for some special abilities on Armor gear. Shadow Hunter gear is double tagged with both symbols, the red triangle and the grey hexagon.
Double tagged equipment are:
Although not tagged but clearly from Shadow Hunters as well:
Also double tagged is the bundle