So, after some testing, I was able to determine the criteria that is currently set in place as of the time of my reply here. As far as this mission is concerned, the criteria is as follows: •Mission must be on Hard Mode •Must not wipe(players can die, but you cannot get the wipe screen) •There IS a FOUR MINUTE time limit from the time that the shadow veil disappears and you can start running, to the time that you enter the third door area and hear Eris's voice again. •Once aboard the ship the secret encounter timer starts upon entering the first room where enemies spawn Hope this helps. If you need help, feel free to hit me up, my gt/psn is KilikMadskillz