Ooo, good idea for a thread. I have a request. I want to use a classic shambling mound. The thing is, my players are very casual, and not familiar with many D&D icons. They won't recognize a shambling mound when they see one, so I need help flavoring it, describing it, and basically understanding it. How would you explain a shambling mound and its place in the world to somebody not familiar with one at all?
Particularly, I'm struggling with the lightning immunity/lightning healing thing, which might seem like a screw-you to my lightning-breathing Dragonborn player. Why is a plant immune to lightning? Anyone want to step up to the pseudoscience bat for that one?
Shambling Mound -
1) Make it a literal Man-Thing/Swamp Thing riff. A man was murdered and his body buried in the swamp. The Shambling Mound rose from that section of swamp, with some strange residue of the man's spirit (like the 'echo' that remains and can be contacted via Speak with Dead, the dead guy's actual soul is gone to wherever). It has images of a wife and a home, which it tries to contact in it's vaguely mindless way, and only succeeds in causing a panic in town.
The people who killed the original man used a lightning spell to finish him off just as he thought he was escaping into the swamp, being evil cultists (Adepts? Druids? Sorcerers? Wizards?). The Shambling Mound will recognize them, and is hunting them down. They killed the man because they were trying to get him to join their cult, and they consist of prominent townsfolk, who are now seeing signs that the creature is following them, watching their homes, etc. These fine upstanding citizens of the town need the adventurers to save them from the beast (one of them has already been killed, as it burst into his home and went berserk), preferably before their secret brotherhood is exposed...
Note that the Shambling Mound is still going to be a threat, even if the cult is exposed and scattered to the four winds (or planted six feet under), as it's not a revenant, it's just a destructive rotting plant monster that has some residual memories from the rotting remains of a dead man contained within it.
2) Hobgoblins were building a fort in the wilderlands on the other side of the woods from a human community. They cut down a druid's sacred grove (killing the druid and his brown bear companion in the process) along with a pair of dryads. The rotting remains of the dryad's trees, along with the body of the druid and his bear, came to unwholesome life after a thunderstorm three nights later, and the Hobgoblin woodcutters were brutally repaid in kind. The Hobgoblins have abandoned their attempt to build a fort here, but the Shambling Mound is still prowling around, and has no particular ability to tell a hobgoblin from a human from an elf. If it's humanoid and around the right size, the Shambling Mound will shuffle forward and attack.
Unlike a traditional Shambling Mound (or the one above), this one *does* have a touch of revenant to it, and if the bodies of the dryads and druid are found and buried with any sort of respect, the creature will shamble forth, shedding leaves and twigs and compost as it moves, until it's last leaves fall upon the new graves.
Maybe a new Dryad tree will sprout from that spot, a year later.