[Discussion] explaining how subaru figured out rugulus authority

So I've seen anime onlies confused on how subaru figured out rugulus authority so I'm gonna try to explain to the best of my ability without spoiling anything

So first of all y'all need to know that Subaru is a star nerd this have been established way earlier in the novel but was glossed over in the anime the only instance subaru's knowledge of stars was mentioned was in s1's OVA this is important because this knowledge is key to how subaru figured out the authority 2nd as it was established subaru was trying to figure out how regulus abilities work that's why he kept analyzing rugulus's attacks but to no avail subaru couldn't figure out anything, that's until this ep because rugulus started attacking using water if you remember until now rugulus was only using debris dirt and air to attack but now that he used water subaru noticed something when rugulus was carrying the cube of water even tho rugulus was moving around the cube of water kept its shape not moving in the slightest like it was frozen in place ( I know that's not how it looked in the anime but that's how it was in the novel ) the same thing happened when rugulus was walking on water normally when characters walk on water their footsteps make waves rugulus footsteps weren't and subaru kept a mental note of that now to the moment of the reveal when Emilia mentioned that rugulus was called little King by his wives subaru noticed that rugulus was a name of a star he made the connection because 1) the star rugulus in our world translate in latin to little king and 2) the other archbishops names match the names of stars too and since betelgeuse names that translate to yaad el jawsaa in Arabic or hand of Gemini(not sure of the term here I'm using a literal translation) in english gave hint to his authority subaru tried to find hints in both the star itself and the naming behind it the hints he found was these 1) rugulus is a fixed star a fixed star means a star that doesn't change its place or brightness meaning that no matter how much time passes the star will still static keeping its place and brightness like it's frozen there 2) rugulus also translates to qalb al Asad in Arabic or lion heart in English 3)rugulus is a part of the Leo constellation which refers to the nemean lion in Greek mythology that's known to be invincible, using all this hints coubled with what he observed from earlier when rugulus used water to attack subaru came to the conclusion that rugulus's invincibility have a relation to his heart and that it comes from him stopping the time of his body

So to recap what allowed subaru to figure out the authority is

1) his excessive knowledge of stars 2) betelgeause name hinting to his authority 3) rugulus's attack being frozen in place 4) rugulus being a fixed star in our world 5) rugulus being translated to both little king and lion's heart

As for how rugulus's ability to stop the time of his body allows him to be invincible that's for next week