From the sneak peak it seems as if the previous keeper of the suns power, before Leona, had a battle with the previous keeper of the moons powers, the moon wielder lost the battle and the second was chosen, probably many years after. Then it almost seems as if maybe she'd trained for years to get revenge, only to find that the previous sun warrior had died in some way, and was paying her respects for whatever reason (It really looks like she's at a burial site, with all the sun markings and ribbons around.) And that she has little hatred towards Leona personally, but is on a mission to avenge her lost sister.

The reason I don't think the two in the mural are Leona/Diana is because of the differences in the armor, it would make sense that a chosen wielder of the power is selected every howevermany years, similar to an Avatar.


Thoughts?

Shameless bump

Only thing I can say about that is, Luna Moonfang.

I will note that you are correct on (at least) one thing: the Chosen of the Sun and Chosen of the Moon depicted in the mural are not Leona and Diana, but their ancient predecessors.

Is Luna Diana's predecessor?

I'd like to add in that it seems suspiciously like the first episode of Friendship is Magic. Just saying.