Millions of years ago, an avian race known as the Rackuddon held the galaxy in their feathered hands. But, as you'd expect, something happened. Exactly what happened remains a mystery. Extragalactic invaders hunting for sport? Societal unrest born of existential dread? Some even claim that pure chance was at fault, causing the perfect accident to utterly and completely dismantle the ancient empire. Regardless of forgotten history, the last remaining Rackuddon resided on an experimental habitat known as a frame world. Capable of being expanded infinitely, given the materials. But the Rackuddon are a luxurious people, unfit for labor. So the Zenak were made, machines that would be doing the heavy lifting of remaking the Rackuddon empire.
Aight, lore out of the way, how do these dudes work? Simply put, they are tall, wide, T W I D E. Rouge servitors that operate out of a single, expandable station and are intent on cramming every single damn pop in the galaxy on it. Now to expand this frame world, you usually will glue on asteroids you find in neighboring systems, you can also use alloy to build new sections, influence to use existing section more efficiently, OR BREAK APART ENTIRE PLANETS AND GLUE THE PIECES ON. Now, the way that last one works there is a technology in the game meant for printing planet sized warships using planetary mass obtained from breaking down planets. Planetary mass which has the secondary use of expanding the frame. Now, one final thing I will tell you, you can never colonize other planets, colony ships can't be built and conquered planet have their pops transferred immediately. Instead, you build outposts which extract tiny amounts of resources, but give buff that build up FAST. All in all I recommend gigastructural engineering for this feature alone!