Macuil is Wind Dragon, so he is an eagle
Indech is Water Dragon and he is a turtle
Seiros aka Rhea is Sky Dragon
https://fireemblemwiki.org/wiki/Crests#Crest_item_availability
I notice Byleth doesn't seem to grow in SPD as Enlightened One
But That is their only weakness
Levin Sword Byleth can wipe out all enemies without high RES and anyone with RES can be killed with normal swords, pretty OP huh?