Having watched the 'movie' of Halo 5 cutscenes, it occurred to me...

That the whole Janus Key plot to Halo 4 never really paid off, did it? Supposedly it was the big 'prize' hidden on Requiem, but Halo 5 makes no reference to it whatsoever. Despite it supposedly cataloging every piece of Forerunner tech in the galaxy, when fireteam Osiris rescues Halsey from Jul M'dama at the beginning of 5, nobody mentions it. While she's aboard Infinity through the whole rest of the game, she doesn't appear to study it. Unless it's how they knew that there was a Guardian on Sanghelios, but if that was the case they could have at least name-dropped the key so that new players (or forgetful ones) knew where the intel came from.

I'm an island- peopled by bards, scientists, judges, soldiers, artists, scholars & warrior-poets.