Alchemist

From HGWiki

The alchemist in town sells dyes, pest repellents, and magical grenades - as he calls these things. Many of his items can also be used to craft traps. He will also craft weapons to change the damage types on them if you have gems equivalent to the existing damage types 1d6, 1d8, 1d10, 2d12, etc. Put the weapon and gems in a bag and use the !forge command then talk to him to make the change assuming you have enough gold to cover the cost.