I honestly don't like Eusto at this point. Like some commenters mentioned, all he has done was look at the Empress with rose-tinted glasses, putting more pressure on her sore shoulders. He claims to be the victim but he wasn't the one who was drugged and lost all control. Not to mention, that melodramatic acting of 'omgeeee why wasn't I strong enough to lead her to the path of LiGHt?! How could this happen to ME??'. Bitch, I swear-
If he had just noted the poison even once, none of this would have happened. Why didn't he do some sort of investigation? Surely seeing someone change so drastically had raised some red flags? He has a fucking secret rebel group. There is a powerful yandere who would do ANYTHING to protect the Empress and not to mention, that genius mage who gathered all that dirt in such a short amount of time.
HE HAS RESOURCES. HE HAS ENOUGH MANPOWER TO TAKE DOWN AN EMPIRE. WHAT. IS. HE. DOING???? Why is he just sitting on his ass, acting like he's some sort of love-struck fool in the misunderstanding part of a romance movie? For a supposed trusted partner who's job was to protect her back, he's doing one hell of a shitty job.
In the end, he's just as bad as the drugged!Empress, since he had been swayed by the words of those rebels. To make things worse, he had a clear mind and should have enough knowledge of the shit a noble would have done to gain power.
I hope the Empress makes him suffer in the pool of guilt he deserves to be drowning in. He has definitely let her down big time and he does NOT deserve her trust.