The first few monsters that they encountered were quite simple; insectoids. Clearly powerful, monsterfied insects or basically anything that you could find hiding under a rock in a forest. Worms, pill bugs, ants; they were massive, almost filling up each of the tunnel's corridors on their own. According to Bree, the area opened up and became a bit wider further in, but they had to get that far first.
As the monsters died, their bodies fell apart and left behind some simple rewards. In the case of this dungeon, it was just some small mana crystals, though. At least here on the first floor. Maybe in later floors, other 'items' would be dropped, but who really knew? Eisen doubted that this dungeon's master set things up for a proper cycle or to give something to intruders. Rather, it probably just used its own presence and power to forcefully increase the dungeon's strength, instead of boosting it step by step by gaining points by inviting and fending off intruders.
