As a lengthy campaign with a number of characters, the following section contains spoilers.
Level 1: Dungeon Level
The Undertakers
A bandit gang composing of failed actors, they disguise themselves as vampires to prey upon gullible adventures who come into the Undermountain by charging them a toll for safe passage. However, by the time the players arrive, the Undertakers' dating leaders, Uktarl and Harria, have recently had a bad breakup that threatens to divide the gang.
- Arc Villain: Of the first half of the Dungeon Level.
- Big Bad Wannabe: The Undertakers may seem like an intimidating start to the Undermountain (by apparently throwing an entire vampire coven at the players), but they're just a group of disorganized bandits. They're also far from as dangerous as the Xanathar Guild on the same floor.
- Classical Movie Vampire: Parodied and Subverted. They run a somewhat convincing act to scare adventurers into handing them their gold without a fight and killing anyone who resists. However, once seen through for the highwaymen they are, there's nothing vampiric about them.
- Uktarl is especially this since Harria has a flesh golem under her control.
- Dirty Coward: Being hurt or having one of his minions killed in front of him is enough for Uktarl to turn running. Harria will only do the same if she loses control of her flesh golem.
- Dying Declaration of Hate: If the two are forced to make their Last Villain Stand in each other's presence, they make sure to vent their hatred of their ex before inevitably succumbing to the players' weapons and spells.
- Evil Versus Evil: The Undertakers are evil, but between their leaders' infighting and the Xanathar Guild, sure have their antagonists before player interference.
- Minor Flaw, Major Breakup: Whatever caused Uktarl and Harria's split has them at each other's throats preparing to kill their ex to take control.
- Never My Fault: If both Uktarl and Harria run to their gang's main hideaway simultaneously to make their Last Villain Stand, they die blaming each other for the gang's soon-to-be destruction.
- Starter Villain: They will most likely be the first major obstacle players will encounter in the Undermountain besides the Xanathar Guild.
- Skewed Priorities: Even when at the mercy of the players, Uktarl and Harria will sooner argue than set aside their differences and work together.
- Women Are Wiser: Harria is the more level-headed and competent leader of the Undertakers, and most likely to win of the two bandit captains.
Fine Fellows of Daggerford
An adventuring party who, despite their name, are a group of evil adventurers. The party consists of a human spy named Kelim the Weasel, a shield dwarf scout named Copper Stormforge, a human priest named Midna Tauberth, and their leader, a warrior named Rex the Hammer. And a half-elf cleric named Halleth Garke who was murdered by the party and became a revenant. The rest wandered to the next level while Kelim left the party.
- Ain't Too Proud to Beg: Midna, should she find herself in a losing battle with the players, will beg and try to let the players have access to her lair's food and wine just to spare her life.
- Arc Villain: Of the back half of Level 1 and the front half of Level 2.
- Asshole Victim: If the players track them down and kill them, Copper, Rex, and Midna deserve their deaths and the horrible situations they find themselves in for Halleth alone.
- Ass Shove: Copper, when he was captured by the Rustborne goblins, hid the group's (inaccurate) map between his butt cheeks.
- Disproportionate Retribution: Halleth called the others out for undercutting the division of treasure. Copper, Midna, and Rex responded by murdering him, looting his corpse, and throwing him in a hole.
- Copper is especially guilty of this trope. Dwarven pride in their beards aside, attempting to murder an entire bazaar of goblins is far from a reasonable response for them hacking your beard off for trying to steal from them.
- Dirty Coward: Kelim doesn't care about the party and has ran off, ending up wandering into a pit where a Grick Alpha slumbers. The players can choose to rescue him and he'll repay them with a spellbook he stole, but that's as far as his generosity is concerned. He will betray anyone for his own survival.
- Fatal Flaw: They have several personal ones, but their biggest, mutual one is Greed. This brought them to the Undermountain, seeking riches based on the stories of Durnan and other adventurers. From there, starting with Kelim's desertion and Hallim's murder, it's what drove them apart to their doom... most likely by the Player Characters' hands.
- Faux Affably Evil: Their Ironic Name Lampshades this. Copper may promise the map, but he's looking for an excuse to kill goblins despite nobody but his wounded pride benefitting from it. Midna has found arguably one of the safest places in the second level for her and only shares to spare her life when it becomes clear the players have the upper hand and is the most guilty of Halleth's murder, stealing his holy symbol. Rex, annoyed by his party's bickering, abandoned everyone to keep adventuring, and repays his rescuers by trying to take over their party.
- Hate Sink: Except for Halleth(and perhaps Kelim, who at least gives the players the spellbook he stole as thanks for saving his life), there's probably not a redeeming bone in their bodies. They murdered their party member, and when encountered, will not hesitate to complicate the players' journey if helped (Copper will go Roaring Rampage of Revenge against the Rustborne goblins for cutting his beard off, Midna will immediately attack the players to preserve her haven, and Rex will try to take over the party as soon as he is patched back up.
- Ironic Name: They're not 'fine' fellows, as they even resorted to killing one of their members.
- Laser-Guided Karma: At least two of them are in peril, with one captured by goblins and the other found outnumbered by two strong fiends. Midna, on the other hand, has gotten into hiding somewhere on the second level. It becomes even more karmic if you bring Halleth, as he wants revenge.
- No Good Deed Goes Unpunished: These guys can and will take advantage of players' generosity by complicating the first and second levels of Undermountain if they're saved.
- Roaring Rampage of Revenge: Halleth desires to kill his traitorous party members who betrayed and murdered him.
- Copper Stormforge wants to do this to the goblins of the Rustborne tribe for cutting off his beard.
- The Starscream: If the players rescue him, Rex the Hammer will wait until he's healed enough before turning on them and trying to bully the players into being his minions.
- Token Good Teammate: Downplayed with Halleth. He served a true neutral goddess, but he was with an evil party. Deconstructed because that's part of what led to his death when he tried to call them out for undercutting him.
- We ARE Struggling Together: Because of their evil alignments (except for perhaps Halleth), the Fine Fellows lacked cohesion, ultimately leading to them falling apart.
- Ungrateful Bastard: Besides Kelim's ability to betray and desert the players if asked to come along (and he does genuinely thank the party by giving them something), Copper and Rex outright repay the players' kindness with almost-immediate Millstone behavior, as Copper will attempt to go on a goblin-killing rampage in the bazaar (and thus separating the players from a key Restand Resupply Stop), but Rex will attempt to take over and bully the party if rescued and allowed to join.
Level 2: Arcane Chambers
Yek the Tall
Yek is a goblin who found a magical circlet that turned him into a tall human. And he's proud of it.
- Humanity Ensues: Thanks to the circlet he's wearing, The Circler of Human Perfection.
Kalabash
Trenzia
Level 3: Sargauth Level
Azrok & Lurkana
Marta Moonshadow
Coral Black, Gurgle Brine, & Caldra Cuttlefingers
Preeta Kreepa
Kinrob
Level 4: Twisted Caverns
Jibber-Jabber
The Alchemist
Darribeth Meltimer
Noolgaloop
Level 5: Wyllowwood
Wyllow
Valdemar
Vool the Outcast
Crissan
Mobar
Level 6: Lost Level
Skella
King Melair
Mornhyld Crystalmantle
Level 7: Maddgoth's Castle
Otto the Faerie Dragon
Maddgoth
Alignment: Neutral Evil
Challenge Rating: Varies
- Cool Helmet: He has in his castle a helmet that grants the wearer invulnerability on all damage as long as it's in his castle.
- Serial Killer: Of mages he lures in his castle to torture and kill, even having records on who to hit next.
Gravillok & his Family
Level 8: Slitherswamp
Yoastal
Agorra Duskaxe
Excrutha & Serakath
Hexacali
Torbit
Kuketh
Level 9: Dweomercore
"Halaster Blackcloak"
Spite Harrowdale
Dumara
Cephalossk the Mind Flayer
Nylas Jowd
Skrianna Shadowdusk
The Horned Sisters
Elan Tanor'thal
Yarek
Level 10: Muiral's Gauntlet
Muiral the Misshapen
House Auvryndar
Level 11: Troglodtye's Warren
Kol'daan
Level 12: Maze Level
House Freth
Level 13: Trobriand's Graveyard
Zox Clammersham
Kurlog
Chanterella
Level 14: Arcturiadoom
Emerosa
The Deformed Duergar
Alussiarr
Level 15: Obstacle Course
Yrlakka
Thwad Underbrew
Kavil Mereshanter
Fidelio
Netherskull
Level 16: Crystal Labyrinth
Al'chaia
Ashtyrranthor & her Dragons
Marquox
Level 17: Seadeeps
Extremiton
Level 18: Vanrakdoom
Keresta Delvingstone
Umbraxakar/Glyster
Portia
Level 19: Caverns Of Ooze
Captain N'ghathrod
Alignment: Lawful Evil
Challenge Rating: 8
- Gameplay and Story Integration: While he wields a sword, he lacks proficienty of it, so he relies on his abilities and spellcasting instead.
- Ninja Pirate Zombie Robot: A Cthulhumanoid Spell Casting Space Pirate.
- Space Pirate: With a pirate outfit and a peg leg, even!
Ichthyglug & Jarûk
Level 20: Runestone Caverns
Ezzat
Floot
Level 21: Terminus Level
Valtagar Steelshadow
Stalagma Steelshadow
Fazrian
Race: Planetar
Alignment: Lawful Evil
Challenge Rating: 16
- Fallen Angel: Numbers of killings of monsters he's sent out to destroy has caused him to crack, becoming a Hanging Judge who will execute those he sees guilty in his eyes, and only sparing those who show willing to sacrifice themselves or courage.
Level 22: Shadowdusk Hold
The Shadowdusk Family
Noble family who were banished from Waterdeep who had made this level their home, corrupted by the effects of the Far Realm.
- Body Horror: Exposure from the Far Realm has messed with the appearance of some of the members, such as Cassiok, who now has the body of a cockroach but with a human head.
- Brother–Sister Incest: Both Zalthar and Dezmyr are siblings and are in love with one another. Hell, there's even a painting Zalthar was working on of his sister in the nude by the time you encounter them in their room.
- Sanity Slippage: As a result of the Far Realm exposure, the family has become corrupted and lost themselves.
Level 23: Mad Wizard's Lair
Trobriand
Race: Human
Alignment: Unaligned
Challenge Rating: 22
- Brain Uploading: His project which involves transferring his soul into an Iron Golem, turning him into the titled Metal Mage. His real body is kept hidden in another room. If either his golem body is destroyed, taken out of the room he's located, or one of his pillars gets destroyed, his soul is instantly transferred back to his old body. If his old body has been killed, well...
- Heal Thyself: He can cast fire spells on himself to recover Hit Points, being in a body of an Iron Golem.
- Mad Scientist
- Pet the Dog: When his discarded, broken creations became self-aware and started their own society he...gave them everything they needed to survive.
- Scary Scorpions: He controls the Scaladar, mechanical giant scorpion constructs with his ring.
Arcturia
Race: Undead
Alignment: Any Evil Alignment
Challenge Rating: 21
- Affably Evil: She can be on friendly terms with the players depending on your actions. Destroying her phylactery, however, will make her drop it and attack them on sight.
- Amazing Technicolor Population: She has blue skin.
- Cute Monster Girl: For a lich, she is rather good looking, which has to do with altering her appearance with her magic.
- Mad Scientist: Of the magic variety, she has a rakshasa locked up to get their blood for her experiments.
- Our Liches Are Different: While being like most liches, she has a more fairy-like appearance and has a flight ability.
Halaster Blackcloak
Race: Human
Alignment: Chaotic Evil
Challenge Rating: 23
- Black Cloak: As is his last name, he wears a black cloak that's a Robe of Eyes, which allows him to see in all directions, 120 feet in darkvision, see invisible creatures, and advantage on perception that requires sight.
- Collector of the Strange: Keeps a bunch of decapitated heads he took from creatures he encountered in the past and reanimated them, keeping them in a secret room in his floor.
- Wizard Classic: Minus the hat, his robe and beard grants him the look.
