Space Creature Mask

Goodie Bags carry it, which puts the entire hunt inside the Halloween window. Bags come off ordinary enemies while the event runs, and each opens into one random costume item, so the sane method is to farm a spawn point, stack the bags up, and tear through them afterward. Three parts means three separate rolls before you have the whole look.

Male and female characters get the identical version, which is unusual for a costume and handy if two people want to match exactly. The tail is drawn from back accessory art rather than the pants, so it hangs behind you the way a cape would instead of following your legs.

It is the Xenomorph from Alien, elongated skull and all. Put it on in a dark cavern with nothing but a torch behind you and the silhouette does the rest.