No it's very logical actually. After the princess is proved to be Allen's child. Sovieshit actually loses his shit and becomes delusional. Taking this opportunity Heinry's friend, the seductive one living in the Eastern empire, takes his revenge by calling upon the bandits who also kidnap the princess.
Well, if I remember correctly (again ), after she was accused of the one owning the infertility cookies, the former Emperor kicked her out. The former Empress tried to assassinate her and was thrown out on the water (sea/river) and was found and rescued in Ergi's country by Ergi's dad. He has kept her since then. I think his dad found out she was the former Emperor's favorite concubine and was kicked out ao he abused her. Because of these experiences she was unable to take care of Ergi. I forgot how Ergi was able to know his mother's struggles or was it even discussed in the spoiler forum but he was taking revenge for the sake of his mother. He probably heard it as a story from his mother since he would go to his mother and tell her everything about Sovieshit and his empire like it's a continuation of his mother's story. I think he was hoping for his mother's closure for her sufferings. The one property he asked as a payment for Trashta's credit before also has something to do with his mom.
ik people said that according to the novel soveshit ends up loving rashta’s baby and raising it as his own but i dont want that to happen ╥﹏╥ not to hate on the baby, but i want soveshit to die alone and miserable!! he doesn’t deserve even a stepchild!!