The Empire of the Lost was a relatively young state that was burdened with a loaded past.
When the Vulcanites initially rose up and rallied their dwarven compatriots from nearby star clusters, their conquest did not happen overnight. Many years passed by as the increasingly more emboldened rebels conquered state after state, beginning from the weakest and most decayed third-rate states to finally breaking apart the once-powerful second-rate states.
The dwarves accomplished all of this while fighting and dying under their unflinching belief in Vulcan and the notion that they were superior to the tall folk!
