hell hound 10
hell hound 5
hell hound 8*
ochre jelly 3
ochre jelly 3
ochre jelly 1
displacer beast 5
giant spider 6**
red dragon 2
stone giant 2
*extrapolating from Holmes, doubled number of fifth-level monsters on sixth level
**extrapolating from Holmes, tripled number of fourth-level monsters on sixth level
****extrapolating from Holmes, quintupled number of second-level monsters on sixth level
Finally, the game’s namesake—dragons! This pair (twins) should have quite a hoard. They use the hell hounds as guard dogs and do not get along with the trolls, who sometimes ally with the ogres. Like gargoyles, the stone giants are already made of rock and therefore are immune to the gaze of basilisk and medusa, and they wander the level with impunity (except the dragons’ territory). The elfs and berserkers sometimes trade when they’re not fighting, and the berserkers sometimes employ the ogres as mercenaries. Also, I think this number of elfs is large enough to earn them a leader (2-4/2-8 fighter/magic-user per their monster description). The jellies wander the corridors in search of food, while displacer beasts and manticores have their own lairs. The giant spiders can serve as guides if the price is right.
We're done here; on down to the seventh level!
*extrapolating from Holmes, doubled number of sixth-level monsters on seventh level
hill giant 7
hill giant 4
displacer beast 6*
fire giant 1
grey ooze 4***
giant spider 33**
hell hound 24*
**extrapolating from Holmes, tripled number of fifth-level monsters on seventh level
***extrapolating from Holmes, quadrupled number of fourth-level monsters on seventh level
****extrapolating from Holmes, quintupled number of third-level monsters on seventh level
Wow! A fire giant—so that’s where all those hell hounds are coming from. Seems like he bosses around those hill giants, and I bet he has some lava to play in, as well. The trolls, of course, steer clear of his neighborhood. With all those hobgoblins, the hobgoblin king and his 1-4 bodyguards (all of whom fight as ogres, per Holmes) will be hanging around too. I’m thinking the hobgobs raise the displacer beasts as pets; the beasts can smell doppelgangers, which prey on the other humanoids. The spiders must know of a secret route from here to other levels; they might trade that knowledge for magic items. Manticores nest here, explaining their large numbers, and the owlbears prey on them. Basilisks have their own lair. The ogres down here are looking for work; they’re on the outs with the hobgoblins. The powerful undead and numerous zombies mean there’s a shrine to evil chaos that corrupted its priests and worshipers, turning them into specters and zombies. The vampires here are victims of a separate curse, feeding on any creature (other than oozes or basilisks) foolish enough to enter their catacombs.
There are some tough critters down here, but they're bound to get even tougher as we descend further.