Also, I have a headcanon that Elwurd's lusus is a scorpion, because so far both ceruleans seem to have arachnid lusii

Oooh, that could fit quite well. Hmmm… What would Remele have? She’s nautically themed and has weird eyes. Maybe a Mantis Shrimp? Do Crustaceans count towards arachnidness? … Are Mantis Shrimps Crustaceans?