After making habitability modifications I can finally stop resettling, but there's a still a lack of population concentration. So my first 3 perks are one vision (for amenity and unity boost) and 2 ascension ones. I am going for a fast biological ascension (the only one available) because it aligns well with habitability modifications. I think that one has to go fairly wide, since swarm needs a lot of planets to grow pops fast.

Initially I am trying to keep population on unsuitable planets to the minimum (1) and resettle them, but it puts a strain on energy income. So the sprawl goes up and research and traditions suffer. Winning the wars is achievable, but it requires resources (alloys+energy) and then what? I am taking the planets to at least have a reasonable pop growth, but the result is that I have rather small population thinly spread across many planets. Despite the swarm military bonuses the war appears to be more challenging than with a regular empire.

It appears that AI is playing more aggressively when facing a devouring swarm. I am literally in a non-stop war, so I can't even disband useless starports I happened to conquer. It seems that every game I follow the same pattern - conquer the first neighbour for food and planets, then someone declares on me, so I conquer them too and so on. I have started playing devouring swarms recently and I am finding it difficult to make them work well.

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