Monster Mash: G is for Gallu!

Those indebted to the fiends of the underworld can expect to be made to pay up but if a powerful enough villain feels crossed or desires an audience, they will send for the gallu. These al-shadim or "faceless ones" come from the shadowy dunes of Hades, resembling dark, featureless and long-limbed humanoids with an expressionless mask adorning their faces but, rarely, will you see these creatures before they make their move.

Shapeshifting and Planeshifting. The main reason that their prey do not see them before the pounce is because gallu are shapeshifters that can seamlessly take the form of any humanoid in the blink of an eye and use all of their abilities while disguised as an old beggar or priest or whatever stranger they take the form of. Their modus operandi, from there, is to stalk their mark, while disguised, and wait for them to be as isolated as possible. From there, the gallu may take some time to research their target and discover the beast means to capture them, but they are impatient; they are more likely to make their move before their victims realize they're being followed. The gallu grabs their target/s, pulling them into their body and transports itself, and its unwilling passengers, to the designated drop-off point agreed to by their masters.