Trader/1.03

Dark Dwarf
The Trader is an incredibly useful building and should be built as soon as you hit tier 2. The skills obtained from the building effectively speeds up the Dark Dwarven economy with faster production of all their core units and an increased resource income. It also offers the coveted Trade skill which the Dark Dwarven player can abuse early on by exchanging their un-needed crystal early game for something far more useful. You will only ever need one of these buildings at any one time, but will always want to have one present for the Trade ability. So it it gets destroyed, then you'll want to rebuild it.