Once I said a group of goblins was a "gaggle of" or a "stink of"
From https://forum.rpg.net/index.php?threads/names-for-groups-of-monsters.349639/
A horror of shoggoths.
A soup of Deep Ones.
A mayhem of PCs.
A grave of Troubleshooters.
A tower of dice.
An arson of fire elementals.
A tsunami of water elementals.
A whirlwind of air elementals.
Alternatively, "holocaust", "flood" and "storm".
A landslide of earth elementals.
A scam of lawyers.
A fodder of orcs.
A bag of swag.
A party of sociopaths.
A keg of Dwarves.
A barbecue of Paladins. (For you dragon fans out there.)
A hoard of gold.
A target rich environment of mooks.
A suicide of redshirts
An Aaaaaarrrgghh! of indescribable things of which man was not meant to know.
A pwnage of GMPCs.
A massacre of Blackguards.
A library of Wizards.
In the Dresden Files, a group of Black Court vampires (the actual undead and completely non-sexy ones) is called a scourge.
What else… Let's see what I can get from the Monster Manual.
A madness of illithids.
A choir of angels. (That one's kinda obvious, at least as old as In Nomine.)
An blasphemy of demons. (Or maybe sacrilege.)
An inventory of mimics.
An infiltration of doppelgangers.
A putrescence of oozes.
A grove of elves. (Especially if they're the Gloranthan humanoid-plant elves.)
An atrocity of [insert really, seriously, horrifyingly evil humanoid race here]. (This one's pretty context-dependent; it requires said race to to exceptionally evil in your campaign, and the one most suited will likely vary.)
An orgy of nymphs. (Hey, I can dream.)
A dungeon of orcs
A warren of Kobolds
An outdoor of ents.
A garden of gnomes.
A pronunciation of liches.
A rustle of rust monsters.
A grove of treants.
A dream of djinni.
My two centaurs.
An excess of tarrasques.
A pack of smoke elementals.
A wretched hive of scum (and villainy).
A forum of trolls.
A quetz of coatl.
A rent of ghosts.
A shoulders of giants.
A school of roc.
A big brother of gibbering mouthers.
A pint of hobgoblins.
A numbing sense of inevitables.
An old woman of spider eaters.
A prince of whales (they're in the Monster Manual!).
an applause of crawling claws
A myopia of beholders
a clot of vampires
A mountain of giants
An abomination of aboleth
A displacement of blink dogs
A corrosion of rust monsters
A malice of yugoloth
A dismemberment of grey renders
An amalgamation of chimera
A drain of strix
A trap of kobolds
A mirage of mimics
A clench of chokers
A procession of golems
A coterie of vampires - always liked that one, which blatantly isn't mine
A creche of magmins
A wreathe of wraiths
A household of Animate Objects
A republic of rocs
A chamber of yuan-ti
A frolic of pixies
A shriek of yrthak
a skulk of bugbears
a twilight of spectres
a clash of poltergeists
a volley of manticores
a gimmick of nilbogs
A flight of dragons
A stench of ghouls/ghasts
A quiver of arrow-demons.
A buzz of stirges
A branch of elves
A potluck of hobbits
A motley of adventurers
A debate of wizards
A drama of sorcerors
A clutter of mimics
A bath of slime.
A window of gelatinous cubes
An eclipse of nightshades
A battery of shocker lizards
A grace of angels [I think I'm rather fond of this one.]
A shriek of demons
A court of devils [Perhaps a choir of angels, a cacophony of demons, and an orchestra of devils?]
A mansion of ghosts
A dark of spectres/shades
A shamble of zombies
A sequence of modrons
A clatter of Kytons
A rampage of Bullettes
A venereal of succubi
A labor of golems
A temptation of nymphs
A keg of satyrs
A terror of night hags
A recursion of phoenixes
A rave of fae (since using faeries sounds offensive).
And from https://timkanebooks.com/2013/01/18/a-stumble-of-zombies-collective-nouns-for-horror/
a stumble of zombies
a coffin of vampires
a howling of werewolves
a bolt of Frankensteins
a tanna of mummies
a cauldron of witches
a clang of hunchbacks
an ectoplasm of phantoms
a haunting of ghosts
a glow of will-o-wisps
a bottle of djinn
a trample of kaiju
a decapitation of headless horsemen
a tinker of gremlins
a hunger of ghouls
a husk of scarecrows
a marrow of skeletons
a translucence of invisible men
a beaker of mad scientists
a lever of henchmen
a scream of victims
a probe of aliens
a circuit of robots
