Played a relatively quick Galactic Civilizations 2 campaign on a medium sized map with a custom science-focused race called the Reptoids.
The full write-up I did for the campaign:
Played as a custom race called the Reptoids with bonuses to scientific research and the korath tech tree (slave labor n' stuff). I played a medium sized map and the other factions were the Terrans (stock faction, diplomatic), Drengin (stock faction, warlike), and the Bunzoids (custom race, cyborg rabbits that breed like, well, rabbits (thus high population)).
My starting position was located in the middle of the other three factions, so I knew I'd be surrounded for the entire game. I wound up colonizing three additional planets (one with toxic atmosphere, the other radioactive).
My first challenge came when the Terrans decided to seize some asteroid mining operations by destroying some influence starbases that kept them within the borders of my empire. The starbases along the border held them off for a time, but their superior numbers eventually prevailed, largely because my ships were slow-moving and I didn't want to pull them from the capital.
The second danger came from the Bunzoids, whose immense population allowed them to basically control the voting in the Council of Planets (space UN). There was one vote to decide where to locate the headquarters of the CoP (and get a huge influence boost as a result) and of course the Bunzoids won after voting for themselves. That caused their borders to expand to envelop one of my planets and I got a message it was threatening to secede to join the Bunzoids. Knowing I couldn't hold onto the colony, I sold it to the Drengins for some cash and technology (it seceded from the Drengins to join the Bunzoids a few turns later).
All the while my empire was short on cash due to running deficits due to interest payments on earlier ship/building purchases, which in turn was causing dissatisfaction among the populace. As a race with a scientific focus, however, I was able to sell off research to minor factions in return for liquidity. I also had an interest in providing some support for the minor factions, for there was a period where the Terrans and Bunzoids were focused on picking off the minor factions. By providing the minor factions with tech, they were better able to resist the other empires, slowing their expansions.
But this era of small conflicts came to an end when the Terrans and Bunzoids went to war with each other, a war from which the Bunzoids emerged victorious. The Terrans capitulated and surrendered all their territory and assets to the Bunzoids, who now controlled roughly 3/4 of the map. Seeking to build alliances and wealth, I began establishing trade routes with the other factions (all while appeasing the Bunzoids with gifts).
Needless to say, the Bunzoids had become a major threat, but an even greater threat emerged soon thereafter. The Dread Lords appeared and quickly cut through the northern parts of the Bunzoid empire with their super dreadnoughts, laying claim to a multitude of systems (among which were Earth (former Terran homeworld) and the planet I had sold off earlier). They then spread out throughout the galaxy, for no fleet could withstand them. They enforced their dominance of space by hunting and destroying every ship, fleet, trade route, and space station they could find, their fleets swarming the galaxy and filling it with death and destruction.
On the plus side, the Reptoid's debts had been paid off by then so they were running a budget surplus. This enabled them to buy ships at will. At first I tried to maintain the trade routes, but it became apparent that they didn't last long and only served to attract the Dread Lord fleets. By this point I had committed to going for the science victory condition, all I had to do was hold on to my planets. I also had the good fortune of a random event doubling the quality of my capital, enabling me to build additional buildings (mostly labs).
Then the Dread Lords set their sights on my capital planet, landing invasion forces which killed billions of Reptoids. After the first attempted invasion, the population on the capital was greatly depleted, forcing me to adopt a strategy of smuggling Reptoids from the radioactive planet colony to the capital, carefully evading the detection of patrolling Dread Lord ships. As it turns out, the plan was successful and while billions of reptoids perished in the final stand, they managed to research the victory technology, winning the game. Huzzah!
The TLDR version:
The Dread Lords appeared midway through the campaign and, through their merciless indiscriminate carnage and conquest, rendered space essentially off limits to all factions for no ship, fleet, or trade route could withstand them or long escape their malevolent notice. Isolated and vulnerable, the Reptoid homeworld soon found itself the subject of repeated Dread Lord invasions... while they were able to repel the Dread Lords, billions had lost their lives in the carnage and it was only a matter of time before they succumbed.
Yet hope remained, for they were relatively close to researching the scientific victory technology, all they had to do was hold out a hundred more turns. Thus a bold plot was developed, to buy colony ships (at a colony with essentially no production capabilities) fitted with a bunch of thrusters for max speed and smuggle additional defenders to the homeworld between Dread Lord patrols, then scuttle the ship upon delivery (for ships attracted DL ships and I wanted to stay under the radar). Bolstered by their reinforcements, the Reptoid homeworld was able to withstand repeated invasions long enough to research the victory tech. Huzzah!
While I'm thinking about it, let me share some of the custom ship designs I've made for my custom GC2 races:
On a side note, here's another random AFF screenshot: