Dead Still. Treat a Putrid Haunt as invisible while it remains buried in swamp muck. Swamp Shamble. Putrid Haunts suffer no movement penalties in marshy terrain.
Slam. Melee Weapon Attack, +5 to hit, reach 5’, one target. Hit: 2d8+3 normal bludgeoning damage. Vomit Leeches (recharge 6). A Putrid Haunt can vomit forth the contents of its stomach onto a target within 5 feet. Along with the mud and sickly bile, this includes 2d6 undead leeches that attack the target on the start of its (the target’s) turn, and the Putrid Haunt gains the same number of temporary hit points. As an action, a creature can remove or destroy 1d3 leeches from itself or an adjacent ally.
(From the Tome of Beasts 5E) These shambling corpses have twigs, branches and other debris intertwined with their bodies, and are fairly covered in undead leeches covering their patchy gray flesh. The smell is beyond description, the putridity of meat exposed to air after years of immersion in sewage.