what about light creatures and terms of endearment in different realms?
imagine islanders calling their significant others bird. or fish. imagine passage guide looking at kids running amock and thinking silly baby birds. imagine an ancestor telling their friend see that manta carrying a boat? that's what you are to me and their friend starting to sob
or maybe imagine prairie and the abundance of creatures there. your extremely talkative and extraverted best friend is a bird. the polite little kid that greets you every time you pass by is a whale. your newborn grandchild is a manatee because they do look like one. your first love is a butterfly and the adults used to call you and your friends jellyfish when you were doing silly stuff as children
or maybe imagine foresters praising their best students and calling them birds because one day, they will surely fly very high. imagine them using the names of all those beautiful and majestic creatures that inhabit (or used to inhabit, before everything went wrong) those lands as pet names for their partners. my whale, my jellyfish. imagine a parent calling their child little crab, playing and jumping around, not a care in the world. imagine these terms of endearment being considered old-fashioned during the industrialisation, and then coming back when people start trying to undo the damage they have caused
imagine valley, where animals are seen as inferior to people, and where no one really calls people they care about these silly things. and yet, there is no word that suits your amazing partner with the most mesmering voice ever better than songbird
imagine wasteland, where whales and mantas have been replaced by monsters made of pure darkness. still, the elderly call the new generations mantas and birds and whatnot, because these children are precious, they are their last chance to get out of this mess. imagine telling your friend bleeding out on the battlefield that they are as strong as a whale and will surely make it, and imagine them calling you a manatee because you are saying utter nonsense
imagine that there are no light creatures in vault, not really, but the day the scholars discover the first ghost manta, every single person in the building is referred to as such
and, even if eden is too much for any light creature to really live there, imagine seeing some passing by sparking hope in a young parent's heart. imagine them calling their newborn a bird, or a manta, or whatever, because they wish for their baby to fly away from this horrible place and have a happy childhood and a happy life in general elsewhere
imagine sky kids calling each other everything nature-related because they love everything and everyone equally. imagine ancestors looking at them and wishing they had done so, too