Fallen Empires are ancient empires that have grown inward and stagnate across many centuries. Despite this, their knowledge is so vast that their ships come equipped with almost every single technology possible, excluding all event technologies and some others. This allows their relatively small fleets (they don't really make any ships until Awakening unless they go below a pretty low limit) to combat the UNoE in the mid-game, where their technology and power is close enough for the Fallen Empire to still match them. While their ships can compete in the end-game, they are easily outmatched by more numerous and powerful ships that bulldoze through their fleets and destroy their worlds.

An explanation of the firsts sections tiering.