An idea that dawned upon me recently: If my PC can create traps (wand of trap creation, covering a pit with a blanket, etc.), why couldn't a monster do the same thing?

Enter: the Kobold trapsmith.

Make it a relatively uncommon/rare monster to encounter, otherwise it could be quite annoying. Essentially, the kobold trapsmith avoids direct combat (unless cornered; attacking it would cause it to panic and run away temporarily) and has the ability (probably every 50d6 turns?) to create a trap on the tile it's on. Additionally, maybe give it a chance to walk to a nearby door, close it if able (ignoring doors with items blocking them), and create a trap on the door. If the PC has an adequate Listening skill, it would have the chance to display "You hear a distant tinkering noise" whenever the kobold trapsmith creates a trap outside of vision, so that the newly created traps aren't a complete surprise; also, a kobold trapsmith creating a trap within the PCs field of vision would have the trap automatically detected (whereas it would be hidden if done out of vision). Also, the kobold trapsmith should be immune from setting off traps (both its own, the PCs, and naturally generated traps) so that it doesn't simply end up killing itself on its own work.

Adding this monster would serve two purposes. Firstly, it would help diversify the types of monsters a PC would encounter, keeping things interesting (especially considering this monster would prefer to attack indirectly using traps, unlike most others). And secondly, it would make it potentially risky to explore a room that a kobold trapsmith was generated in, as there might be traps on a square already explored by a PC (not to mention in narrow corridors).

Besides, SOMEONE must be building all those random traps the PC encounters during his adventure... ;)

What do you think?