Not-quite-undead lifeforms reborn from mobs that died of the DTs — sore-covered, mindless, and driven to devour and gather.
Festering Ghouls are what the floor's drug addicts become at the end of the DTs. Withdrawal from the Rev-Up shots first brings violent tremors (stage one, killing half); survivors either reach stage two (the strength-doubled Babababoon-style rage) or drop dead — and the dead soon transform into Festering Ghouls: moss-and-sore-covered, bark-skinned, plodding things that fill Station-Repair-Hub-E by the thousands. Critically they are NOT undead but new lifeforms in old shells, so anti-undead attacks fail (a double-tap is still wise, as Widget learns fatally when a 'killed' one revives).
Born knowing how to reach the yards, they exist only to devour organic matter and gather more of their kind — and when enough amass, something 'awful' is meant to happen. Nastier 'Wrath Ghouls' sometimes break their transport cages.
Plodding humanoid mobs of many former races, covered in oozing sores exposing bone (bark-skinned ones look shot full of holes); moss-grown, mindless in gait though some can still speak.
The end-state of the floor's drug addicts — a gathering ghoul swarm building toward some hidden critical mass.