What's really disappointing (or maybe shows how little the Emperor actually can do, and we have been protected by Orpheus specifically all along - except why does the choice to "betray" him between Act 2 and 3 result in an immediate game over?) is that...

...if you get the scene where he reveals he was mind-controlling Selmane and the Knights of the Shield, he explicitly says he will do the same to the PC if they keep going against his intentions. He never follows up on said threats unless you count him flipping allegiances to the Netherbrain on a whim.

Overall, though, I consider him to be one of the weakest parts of the plot and the obnoxiousness with which he attempts to "guide" borders on patronizing (especially early on as he comments your misses and combat choices). Not to mention that the guardian's introduction switched from a dream of temptation to a pretty much 1-to-1 retread of the D:OS 2 plot which made me worried Larian were just re-using that whole narrative. His attempts at flirting and the overall tone his interactions take in Act 3 all feel extremely forced and artificial (which could be intentional, given he's an illithid? But the fact that he does it without prompting and regardless of your romance status is ever-so-slightly uncomfortable. His writer must just have a thing for shirtless squid-men...)

The whole...

...Balduran tie-in...

...was most unnecessary and I would prefer to ignore it as non-canon, honestly, alongside some of Beamdog's story beats from their games.