The Dwarf is a valley resident that lives in the mines. At first, they will speak in Dwarvish, which is unreadable for the player, and only after translating some scrolls will the player be able to communicate with them. The actor/ress should be able to improvise as they need to voice some lines in a made-up language, but there is no indication of how the Dwarf should sound like, so you can totally go crazy on how you interpret them. The game's code states that the dwarfs' gender is 'undefined' so anyone can audition.