To quote the orb directly 'that he'd have to live forever with what happened'.

There's a lot we're missing, but to be frank... Every mission we've been on, we weren't able to learn as much as we wanted. But we still had to make choices and act anyway.

[And somehow, all of them are still alive.]

If you're in Taeum... can you see what you can learn about the Highest One? Has anyone actually spoken with them?