The Mithril Factory produces Mithril, which is needed for building and upgrading rooms now, as well as crafting equipment’s sets. Mithril produced is stored in the Mithril depot.
This room is only available at throne room level 11.
Production of Mithril appears to be slowest of all the production items.
Tip: When you hit throne room 11, build the mithril factory and upgrade it to maximum since you will need plenty of Mithril for gameplay beyond this point. Remember to level up your depot along the way.