I’ve thought so since the end of S1 as well- Plants is very family oriented.
Even though Chase might have stopped himself from using the Arcus Tempus out of a sense of duty and to honor Bern’s last wish, I can fully believe that the first timeline’s Plants (the ‘mad king’) more or less went down the deep end after his mother killed his younger brother and father to seat him on the throne. I think he probably used the relic to go back to before Kalian’s 16th birthday, as he sees it as the moment that ‘everything started going wrong’. I’m excited to see where Kalian’s confession goes…
I don’t trust his original brother tbh. Something is off about him. But I agree I can’t wait to see how he goes about this.
My theory is plant used it to reverse time to bring bern back as his own brother. Probably because he didn’t want to be king or some other reason we didn’t learn yet. That’s the only reason that makes sense to me fr. Especially bc his brother didn’t use it for him.