Before any guardian, you have to cut through the ordinary monsters that fill every depth. Here are all twelve: what they look like, what they're good at, where they live and how to deal with them.
The skeletons
Caldria's restless dead, met in nearly every zone.

Risen Minion
Bone · melee
The rank and file of the dead, rising from their graves in packs. Little life, but quick and never alone: don't let them surround you, and sweep them with an area skill.
❤ 26⚔ 4–7Speed 4.6XP 6

Bone Warden
Bone · melee
A horned-helm guard with an axe and a great shield. Twice a minion's life and a heavy hand, but slow on its feet and slow to swing: step back as the axe goes up, then strike.
❤ 60⚔ 7–12Speed 3.8XP 12

Grave Stalker
Bone · melee
A red-hooded cutthroat with twin blades: the fastest of the skeletons and the quickest to strike. You won't outrun it, so turn and fight.
❤ 34⚔ 5–9Speed 5.6XP 9

Ash Necromancer
Bone · ranged
A wide-brimmed bone sorcerer that keeps its distance and hurls green bolts. Fragile: always kill it first.
❤ 30⚔ 7–11Speed 3.6XP 11
Spirits
What lingers once the body is gone: only grief and spite.

Mourning Shade
Spirit · melee
Grief given shape, drifting without a sound and rushing you in numbers. Most common in the Vaults of Sorrow.
❤ 30⚔ 5–9Speed 5.2XP 10

Skull Wraith
Spirit · melee
A spirit wearing a skull for a face: sturdier than the shades, and the first spirit you meet, already in the Ashen Crypt.
❤ 40⚔ 6–10Speed 4.4XP 11

Choir Zealot
Spirit · ranged · Shadow
A masked zealot of the Bone Choir that hovers at a distance and casts shadow bolts. Found in the Pits of the Bone Choir and the Ember Depths.
❤ 30⚔ 7–11Speed 3.6XP 11
Beasts
Things that crawled up from the furnaces and deep water beneath the city.

Cinder Imp
Beast · melee
A tiny devil out of the ossuary's furnaces: the least life and the fastest feet in the game, coming in swarms. Area skills drop them by the handful.
❤ 18⚔ 3–6Speed 6.2XP 5

Pit Fiend
Beast · melee
A great horned devil: the hardest hitter among normal monsters and worth the most XP. Beware when it comes with a swarm of imps in the Ember Heart.
❤ 70⚔ 8–14Speed 3.9XP 14

Drowned Fiend
Beast · melee
A sea-blue fiend dragging itself up from the drowned catacombs, club in hand. Nearly as tough as a Pit Fiend; hits hard but slowly.
❤ 64⚔ 7–13Speed 3.7XP 13

Abyssal Squidle
Beast · ranged · Cold
A bat-winged horror from the deep water that spits frost bolts from afar. A hit slows you for 2 seconds, so keep moving.
❤ 28⚔ 6–10Speed 3.8XP 11
Slimes
What festers in the still water of the drowned catacombs.

Mire Slime
Slime · melee
A one-eyed spiked blob with the most life of any normal monster and the slowest crawl. Hit, step back, repeat: it can't keep up.
❤ 80⚔ 6–10Speed 2.8XP 12
Numbers are base values at depth 1 (❤ life · ⚔ damage · speed · XP). Monsters grow stronger the deeper you go, and some spawn as Magic (blue) or Rare (yellow): tougher, harder-hitting and with better drops.
Every monster's stats → · The seven guardians →
Skeleton models from KayKit Skeletons and zone monsters from Quaternius' Ultimate Monsters (both CC0).