Thanks - here is today's go at it, using local light sources. I would do the border hulks as if lit by the galaxy itself.

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In the Erhn region of the Imperium, an ancient structure partially surrounds an otherwise nondescript white dwarf, like a partial Dyson sphere. The construct remains intact and electrostatically charged, but its original function is unknown. To the Imperium, it is known as the Coliseum.

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Imperium praxists engineer creatures, including sentients, into biomechanical spacefaring exhibition warriors. Within the confines of the sphere, an orbit lasts a few days; gladiatorial matches often take weeks or months, as spectators come and go. Part of the combatants' biomechanical augmentation often involves altering their perception of time so that, to them, each fight is a fierce struggle for life or death. There is no better symbol of the Imperium: technologically advanced, aggressive, and without restraint.

I wrote about one such gladiatorial match here, about a battle between fighters known as The Kite and The Worm.