Here's the list of critters I ran across on my travels through the Abyss last night, including stats for a few of the new ones.
I'm sure this list is incomplete. I believe some of the areas I ran through have spawn that is supposed to "evolve." Don't quite understand yet the mechanics of how that happens or what you will see when it does happen. Also, I didn't get to go inside the two "peerless" areas. And I didn't stick around the champ spawn areas long enough to see what you get with the next levels. Maybe someone else who has done those can provide further details. All I know is one is referred to as the "Abyssal Infernal" and the other is called, "Primeval Lich."
#1 - Fire daemon.
#2 - Silver sapling room. No spawn.
#3 - Bone mage, rotting corpse, skeleton, spectre, zombie.
#4 - Bone mage, rotting corpse, skeletal knight, wailing banshee.
#5 - Rotting corpse, skeletal knight, Skeletal Lich, wailing banshee, zombie.
#6 - Wisp.
#7 - First time through the area: Fire daemon (regular and Renowned). Stats on the Fire Daemon (Renowned): 1478 hit points; 1199 str, 206 dex, 202 int; 159.7 barding difficulty; 78/60/57/100/50 resists; 50% physical, 25% fire, and 25% energy damage with 22-29 base damage; 98.8 wrestling, 95.5 tactics, 132.6 resist, 40.7 anatomy, 97.1 magery, 91.8 eval, 45.4 med; no preferred food or pack instinct.
#8 - Homunculus that always seems to spawn with a name of "Garamon."
#9 and #10 - Fire daemon, lava elemental, lava serpent. Lava Elemental stats from one loring: 266 hit points; 510 str, 191 dex, 397 int; 107.7 barding difficulty; 67/29/28/100/41 resists; 10% physical and 90% poison damage with 12-18 base damage; 71.7 wrestling, 94.0 tactics, 101.9 resist, 12.8 anatomy, 90.1 magery, 92.6 eval, 102.8 med; no preferred food or pack instinct.
#11 - Fire ant, fire daemon, hell hound, lava elemental, lava serpent. I believe the fire ants are quest creatures. They sometimes drop as loot an item called "Seared Fire Ant Goo." It is not blessed (for now?) and looks like it could be used for decorative purposes; however, I suspect it is actually intended to be a quest item. Fire Ant stats from one loring: 299 hit points; 225 str, 108 dex, 25 int; 76.0 barding difficulty; 52/96/36/40/36 resists; 40% physical and 60% fire damage with 15-18 base damage (they spit fiery goo that sticks to anything in the area); 75.4 wrestling. 77.2 tactics; 53.1 resist; 8.7 anatomy; preferred food is meat and no pack instinct.
#12 - Enslaved gray goblins and enslaved green goblins.
#13A (Fel Champ Spawn Area #1 through the red gate) - 1st level of spawn: Chaos daemon, familiar. (Familiars look like grayish horde minions.)
#13B-H (Fel Champ Spawn Area #2 through the silver gate) - 1st level of spawn: Vampire bat, gore fiend.
#14 - Coil
#15 - Patchwork skeleton, skeleton.
#16 - Giant serpent, lava snake, snake.
#17 - Giant serpent, silver serpent, snake.
#18 - Coral snake, giant serpent, silver serpent, snake.
#19 - Giant serpent, silver serpent, snake.
#20 and #21 - Giant serpent, hydra, maddening horror (and whatever necro summons they bring, e.g., revenant), snake,
#22 - Second stop at this location: Fire ant, lava lizard, lava snake.
#23 - No spawn in immediate area.
#24 - Acid slime. The spawn extends up through the whole area in tan. Most are just ordinary "acid slime" but some appear to be the type that can be used as a dye tub. Colors I noticed on a quick run through the area: Light Tan, Champagne Red, Dark Blue (?).
#25 and #26 - No spawn whatsoever in the deserted and ruined buildings on the west side of the chasm or in the central room. No spawn in the buildings on the lower east side of the chasm. Did not check in the buildings north and northeast of the Slasher of Veils.
#27 - The Slasher of Veils. Did not get a chance to lore him. Read Calvin Crowner's comments about how he cannot be beaten. When you approach, you are frozen in place and see this message, "Terror slices into your very being, destroying any chance of resisting Slasher of Veils you might have had."
#28 - No spawn in the immediate area.
#29 - No spawn in immediate area.
#30 and #31 - Home of the Stygian Dragon. A blacksmith NPC named Manfred the weaponsmith stands in front of the building, slightly to the east.
#32 - Fairy dragon, forgotten servant, wyvern.
#33 and #34 - Fire daemon, lava elemental.
#35 - No spawn in immediate area. To the east are daemon, greater mongbat, imp.
#36 - There are several groups of spawn in this area to the west of Sutek's home: Clan Ribbon plague rat; Clan Chitter Tinkerer; Clan Scratch Savage Wolf; clockwork scorpion. Stats for the Clan Chitter Tinkerer (one loring): 2039 hit points; 339 str, 242 dex, 259 int; 160 barding difficulty; 23/21/49/19/17 resists; 100% physical damage with 8-10 base damage; 84.9 wrestling, 64.6 tactics, 88.8 resist, 13.2 anatomy; preferred food is meat and no pack instinct. These are like glorified ratmen archers.
#37 - No spawn in the immediate area of Sutek the Mage's home. I found him to the NW of his home, up a long corridor that was partially lined with white plants.
#38 and #39 - Daemon, greater mongbat, imp. Edited to add: Went back tonight and also found pit fiends and balrons. One of the balrons was "renowned" and had these stats: 1988 hit points; 973 str, 159 dex, 231 int; 160.0 barding difficulty; 47/26/19/67/40 resists; 60% physical, 20% cold, and 20% energy damage with base damage of 22-26; 92.1 wrestling, 82.4 tactics, 91.6 resist, 2.9 anatomy, 96.7 magery, 97.8 eval, and 92.8 med; no preferred foods or pack instinct. I believe this is one of the areas with "evolving" spawn.
#40 - No spawn in the immediate area. Above it you will find fire daemon, lava elemental and what looks like a fire elemental but was named "error" when I went through. May be a fire ele on steroids, possibly called a "greater fire elemental." (It caused my character's one and only death running through the Abyss, so eventually I'd like to know what the darn thing is supposed to be called. LOL)
#41 and #42 - No spawn in the immediate area.
#43 - If you can proceed past the Guardians, you'll find Silver Serpents, Undead Guardians, and other inhabitants of the Tomb of Kings.