User blog comment:Stabber ApSig/Mass Relays Gone, ME3 ending/@comment-76.178.25.200-20120311031854/@comment-1388547-20120313023759

In Arrival, it was the relay exploding. Either the Codex or Dr. Kenson (I forget which) tells you that destroying a relay would liberate energy similar to a supernova. (Yikes!) I'm hoping that the in the ME3 ending, the relays destroyed themselves in some kind of controlled fashion that put most of the energy into something that only interacts weakly with normal matter. Otherwise a lot of people's homeworlds, Earth included, are toast. :-(