After watching and pausing the trailer at spots of curiosity several times, to me the light phantoms that come down by Elidibert all have radically different gear, though a lot of it is recognizable but seems to be coordinated glamour... I kind of wonder and sort of want to say that the secret trial will be a mirror fight for everyone who enters. We know they have the ability to scan our characters and create clones on the battlefield as early as Achamoth in Lost City of Amdapor Hard Mode, so that would be phase 1. Then Phase 2 would be the real boss, maybe Elidibert siphons up their dying souls, where the souls are shining brightest similar to what Moenbryda did to ensure Nabriales's death, only this time it's to juice up Elidibert.