Your Dwarves have +2/+2
Deepstone Mine is a Level 3 treasure in Storybook Brawl.
This treasure would be a must-have for a Dwarf build, unfortunately there are currently few Dwarf characters in the game and no Heroes with a particular affinity for them in the early game.
Deepstone Mine is rarely worth picking for the long term, however if you have a Dubly or two them it can work well with them.