A theory about 7.3 AQ

The Pyro gnosis is found. Anastasya and the Shades realize they share the goal of bypassing the restrictions put on the world by HP, so there's no reason for further hostility. Aether and Tsaritsa are both connected to the 3rd Descender, Aether being a Descender himself and Anastasya for obvious reasons. Therefore, the only way to break Phanes' Fate system, embodied in the Gnoses, is for the seven archons, each with their Gnosis, to perform "love" on Aether as a sort of "3rd Descender equivalent".

Anastastya's Cryo possesses Time manipulation powers, which means time loop shenanigans. Aether is transported to the distant past, a la Columbina, and to his shock, realizes that he was the 3rd Descender all along. The reason why Anastasya memories of him were wiped is so that she can't recognize him in the present, disturbing the time loop. Aether returns from the time loop and Anastasyas' memory is restored, Aether gaining the Elemental authority of every element. He then defeats Phanes with this power, freeing the Shades, including Ronova, from their duties. Happy end!