Skeleton Key creation price: 10,000

The rouge like dungeons are the ones that require skeleton keys to enter.

https://grimdawn.gamepedia.com/Challenge_Dungeons

Log, the final boss of vanilla does not do this. You might be referring to Karroz (first phase human, second face tentacled monster) or Ilgorr (giant skeleton-like monster, simply resurrects himself once). If it’s the latter you’ve already been inside one of the rogue likes, The Steps of Torment. :wink:

Edit: I also found it useful to check the level-ranges of the rogue-likes. You can do see them on the Grim Tools map. The highest lvl for Steps is 50 on normal/vet, so you’ll have an easy time if decide to go in now.