I swear, some of the creepiest stuff that Valve came up with for HL2 ended up on the cutting room floor.
This is the Cremator, an unused NPC from Half-Life 2. Their role in the game was supposed to be some sort of janitor for City 17, clearing the streets of dead bodies with their “immolator”, a large cannon that sprayed a green beam of acid/plasma which disintegrated organic matter on contact. The pokeball-looking thing in their abdomen was supposed able to connect to the immolator at certain points, giving credit to the theory that the acid the immolator sprays is the Cremator’s own (genetically enhanced) stomach acid.
Like the Stalkers, the Cremators are humans that have been physically and genetically modified. The original human was probably beheaded at some point, as Cremator heads were to be assembled in a factory by children (before they too were scrapped). Lacking the ability to speak, the only noise they made (that wasn’t from the immolator) was heavy breathing
Their sound files/models can still be found in the HL2 game files. One guy got one up and moving.