Comment by anelia perdana on Introvert

Perez who has been slowly poisoning the Emperor since he entered the palace. You remember the time when Tia’s debutante was going to be held and Emperor summoned Perez to his palace telling he will make an entrance with Perez and Perez was going to decline but he heard Tia will be there (I may be wrong about this part because my memory is a bit hazy) and he thinks how idiot the emperor is for drinking alcohol which will kill him soon. 

So it's Perez who has been poisoning the Emperor all along but then he shifted the blame to Empress and her maid falsely testified that it's Empress who told her to poison the Emperor that's when Empress is thrown in the Dungeon and locked forever.