During the first stage animation, Demogorgon and Paranoid Delusions spawn and attack

cooljinx

While any member of the trial team is watching the first stage animation, the players who skipped the cutscene are attacked by Demogorgon and Paranoid Delusions with the delusion debuff stacking while the blue well is not being created yet (it spawns, with rifts, when the last player finishes watching the cutscene). The other two stages do not include the pre-cutscene boss spawn (although paranoid delusions spawn all the time) so I don't see why the first one was designed differently, adding quite more strain to tanks and healers.