Yes, the Dyson sphere looks like a useful megastructure indeed, perhaps the most useful one.
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The Wessari First Speaker, upon hearing that the new "Great Khan" has a diplomatic transmission for all denizens of the galaxy, prepared to endure the usual screeching and hostile insults typical of the Endurga. What he saw instead, shocked him.
This corresponds to my own experience. I, too, expected the usual Raxicodium-level confrontational stuff. Good job to Paradox writers for subverting my expectations and making me feel some sympathy for the Khan and his people.
Far more shocking, however, was the appearance of Edurga troops in the new Wessari acquisitions.
The Wessari fleet numbered around 10K at this stage. It was clear that the Khan is determined to conquer as many stars and planets as possible for his people. With a heavy heart, the Frist Speaker signed a formal submission to the Khan.
In retrospect, I could set my fleet to "allies take point" mode. The Khan's troops were weaker than the Star Entente Federation, in total. But I didn't notice this option yet, and the Khan was threatening to nullify my annexation of the Tiyal lands.
Unfortunately, the two other members of the Federation disapproved of the Wessari decision, with the result of the Federation now continuing on without its founder.
It also kicked me out of the Sek-Lokkar war, preventing me from any potential gains from it.
Still, the Great Khan, was, by all accounts, a truly remarkable individual, both in his palace and in battle.
Frustrated with the war ending, the former Zaxxoid admiral in eternal Wessari service unsuccessfully attempted to defeat the annoying strange hive in one of the Tiyal systems.
Only then the Wessari thought to ask the Curators about the Hive.
Once the Khan conquers a system, it automatically "de-surveys" it, to prevent the player from just regaining it outright with a construction ship. The Khan's own construction ships, however, do not need to survey a system in order to claim it. Such is the way the Khanate gains territory.
Many Wessari were forced to join the Khan's battle fleets. Granted, since the Khan cared about her soldiers and paid well, it wasn't that awful a predicament.
Furthermore, the Khan didn't mind her subjects declaring war on other nations who were not her satrapies, allowing the Wessari to restart the war with the Sek-Lokkar.
Unfortunately, many Sek-Lokkar systems were already conquered by the Wessari's former Federation.
Still, not only the Wessari managed to conquer the Sceptum system and its associated planet, they also claimed the Cador system right under the Great Khan's nose - her ships just couldn't be everywhere. The Khan, strangely, didn't attempt to mind it - maybe it amused her?
In fact, the Khan's troops even helped the Wessari defeat the Sek-Lokkar.
Even as a Satrapy, the Wessari managed to gain land.
Luxuries were distributed to the newly-conquered planet to ease the transition for the inhabitants.
The Khan's Voidfarers managed to defeat a bigger fleet of the genocidal Alvothari.
However, the Draipol proved to be a harder nut to crack...
Still, the Khan rebounded from this defeat. It was a honor for many Wessari to fight the Purifiers and win.
However, it appeared that the Khan has bitten off more than she can chew when she started to antagonize the Mechazur robots. In fact, their war with the Khan saw Mechazur echelons move out of their home systems...
The result was not surprising. Even the Khan couldn't fight a force almost 5X her fleet's strength. The tale of the Khan's defeat would be immortalized across the galaxy in tragedies, where the Khan's hubris was presented as the cause of her downfall. She just couldn't believe that her fate was to be defeated by Helperbot O5.
Khan Musseg, the Great Khan's successor, while clearly talented, was far from being as remarkable an individual. He had problems holding his nobles together, much less keeping the Wessari as a satrapy.
With the Wessari satrapy status ended, the Vun-Okons of the Draipol and the Velutari were only too happy to have the Wessari as members of the Star Entente, again.