Maybe spoiler also please keep in mind that this is only my opinion on the story and what I got from it so far!
I believe Ellie is the treasure the mother stole but I think it’s more likely recused I thought this from the beginning when they talked about her green eyes and even though she looks a little like the king she could also be the duke’s wife that died in my opinion I could be wrong because it’s not revealed yet the king toke the duke’s wife and locked her up in the treasury for her powers the Ellie’s mother who looks like the queen broke in and helped save the mother and could only get to save the baby so rumor went around that she stole the “king’s treasure “ is my guess but will see
My thoughts are similar.
I do believe the duke's wife was kidnapped by the emperor and is the concubine kept in the treasury. I don't think Ellie is the treasure she stole, well not entirely. If she was the emperor would definitely be looking for a baby. I think what she stole was the Duke’s wife. As the thief mom looks like the empress and possibly her sister she may have been friends with the Duke’s wife and was trying to rescue her. Then I think either they managed to escape for a while, and Duke’s wife discovered she was pregnant. Gave birth and then was died giving birth or recaptured. The emperor killed the thief mom to silence that she knew about the duke's wife and for daring to steal from him. The other possibility is what the thief mom "stole" was the duke's wife's power (possibly given to her), and that power became a baby. Like she has the world tree's power and you can grow another world tree with a seed or branch.
Somewhere in that aspect but even if you have the seed or branch without the power nothing will grow I believe that’s why the wife was kidnapped u could be right on the wife leaving before getting pregnant or birth since nobody knows about the baby nor are they looking for her or maybe they think they both died ? It takes to long to upload I can’t wait to find out
Okay I’m on ch32 and lowkey I think vassals’ concern about Ellie being the most notorious thief’s daughter is valid. Like it’s not even about her being commoner and marrying to high nobility is the issue, but her mother literally stole the emperor’s stone. Like yes that ain’t her fault, but declaring her as daughter-in-law is literally openly challenging the emperor. The duke acts like vassals are annoying and he knows the best, but it’s natural that vassals wouldn’t be happy about it thinking it would backfire badly. Their attitude might not be the best, but I am with vassals sorry (except that snaky viscount he can eat shi)