The planet with their giant super important simulation was being eaten by it (and might still be eating it, we only decoupled it from the sun)
I'm kind of surprised they haven't telaported onto it and tried shutting it down or converting it into something to nullify the sun like in the future that they attempted to make, and you gotta admit it'd make an interesting strike :p
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Probably oversight Why does Taeko's fireteam practically suffer the same fate as Eris' did? Why do Red Legion Cabal have different helmets from the dead ones used as props? How did Vance go from a blind prophet to a rabid knobslobber?