Spoiler text.
Also agrona still have forces much more stronger than scythes who's sole mission is to fight against asura (dragon).

I hope this is the correct way to use spoiler tag
Note that this is a spoiler, do not read if you don't want one.
1. About agrona possessing circe, that was a lie by Arthur, sylvie was the one who was possessed by agrona.
2. In the future, its known that agrona can practically tell what all alcryan are doing ni matter where they are cuz of the emblems, regalia and crest they have on there body, that's why agrona always have the latest info on dicathen cuz his soldiers are there, and yes he can forcefully command them to attack against there own will, if they refuse they die instantly.
3. Circe is the main cause of Eleanor downfall as she created a part that led to the elves forest (although she died immediately she inscribed the last mark), this led into Eleanor been captured by the enemies and the elves were treated like slaves.
4. Due to one or two unfortunate incidents, Arthur ends up in alcryan as a half human half dragon and found circe brother by a stroke of luck, though he hated him at first and basically wasn't good to him a first, in the long run he taught the boy and his friends magic cuz he was impersonating as a teacher in alcryan, and he also got help from a lady known as caera who was a scythes disciple (by scythe, i meant our beautiful *scythe series vitra*).
5. That's all I can tell you about circe and what her action eventually caused in the long run, and also the asura came to destroy (wipe away from the map) Eleanor cuz of the alcryan forces. Unfortunately Arthur's sister was in Eleanor then also impersonating alacryan, but due to her bear, the phoenix artifact that Arthur gave her when she was young, her bear and an artifact that also transport people to the hideouts of the remaining dicathen forces she survived, Arthur saw all this when he was in alcrya due to him now been able to manipulate aether and a stone (lyk a relic or artifact).