#aymr

Aymr (the OC character appearing in Ch 15 of the above fic) is my theorized alternative. The Agarthans got wind of Rhea’s homunculi creations (Sitri and her predecessors) and used similar means in combination with their stockpile of Nabatean blood to farm new materials for Crest Stones and weapons. (We know they had Nabatean blood because of the blood reconstruction surgery experiments on Lysithea, Edelgard, and their siblings.) Therefore, Agarthium is the bones and the artificial stones are the hearts of these demi-Nabateans. Aymr is literally the person who would be killed to create Edelgard’s legendary axe post-timeskip. These artificial stones were then used to further experiment upon and empower the Agarthan ranks, as supported in-part by the canon scene in which Solon crushes the stone in Kronya’s chest to cast Byleth into Zahras. (I thought this was a heart, but I went back and watched the cutscene like 5 times after someone on reddit pointed this out, and it’s decidedly not a heart.) In Three Hopes, the scene where Solon is used to open Zahras does not contain a depiction of a stone being destroyed, only him being stabbed. So my conclusion is that any heart-destroying death could be used to power this spell, but Kronya's death required the destruction of her stone, suggesting she, like Sitri and Byleth, is using it as a replacement heart. I posit that this is one of the reasons she's more openly unhinged than her compatriots, who were more likely to be the ones performing the experiments than undertaking them on their own bodies.