Man, I just finished volume three, so I'm all up in the character dynamics right now. The central figure is obviously Frost Deimos, the retired adventurer reborn as the dungeon core. His whole schtick is being absurdly pragmatic and engineering-minded—he's not some ancient evil, just a guy trying to build a sustainable ecosystem of death to protect his soul. Then you've got his primary creations, the dungeon's lieutenants. Kael is the first, a stoic undead knight who acts as the dungeon's warden and Frost's sometimes-conscience. Myla, the frost spirit nymph, is more interesting to me; she's the heart of the place, curious and emotional, almost like the dungeon's daughter.
Outside the dungeon walls, the human side is mostly driven by Elise, a noble's daughter and rising-star adventurer who first 'discovers' the dungeon. She's determined to unravel its mysteries, which sets up the classic explorer vs. architect tension. Her party members, like the cautious mage Roland, get fleshed out later. The real wildcard is the demon prince, Ashrael, who sees the dungeon as a rival power base and a threat to his plans on the surface. His scheming adds the necessary external pressure that forces Frost to evolve beyond just trap-building. Honestly, the roles are pretty clear-cut, but the fun is in how their perceptions clash—Frost thinks he's running a defensive fortress, everyone else sees a legendary treasure vault or a cataclysmic threat.