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
-
The Vex are playing chess. The Red Legion were playing Checkers. The goal of the Vex are to be the last species standing at the end of the Universe. Anything that doesn't serve that end is expendable. If Ghaul is willing to destroy the entire solar system and a dormant Traveller WITH it[b].....why would the Vex want to stop them? [/b]Shit, the Cabal are doing the Vex's work FOR them. Since our Light is one of the few thigns they can't understand....can't simulate...and is a prime threat to the success of their ultimate goals.