They're just trying to figure out what's going on with Sathea, and why one some people are drastically changing, and why some people are uncannily similar to the ones in their blurry memories.
Sephnit is so glad that they're able to live in the sea, you really don't even know the half of it. They've got it even better, too! Their home -- territory? Yeah, sure, they like that -- is the ruins of some civilization or another. They never really bothered to look into it. What matters is that it's theirs, and it's beautiful, and there's so much pecking room for them to store stuff.
They don't have a problem, you do.
Anyways, naturally they can't keep everything they'd like to remain in their possession underwater, so an abandoned little house on a nearby shore works for the other stuff.
Sephnit has no biological family, but has adopted Finn.
Sephnit considers Abel and Mariposa to be their friends, and is trying to figure out what's up with Oblivion and her 'species'.
Sephnit is a long, serpentine dragon with a horseish face. Their body is blue-grey while their stomach, the webbing on their wings, and their "paw" pads are a dark iridescent green.
Reminiscence A Suspicious Place Ancient Aliens Touch Tone Telephone Sundial
Okay, but really, isn't it kind of weird how some people just keep on changing, and the whole world is none the wiser? They've been keeping some track of Mariposa, and while these past few versions of her weren't really.. friends.. with them, they don't just want to let go. So having Abel keep the one eye they have on her is perfectly fine, right? Right, they knew you'd understand! It's also to just keep track of how she changes. Her appearance, her personality, her meetings and falling in love with the same guy, over and over and over and over and over... You get the point. Clearly someone likes her, and it's not just the purple guy.
They still hold onto the radio one version of her gave to them when they were friends. They'll be damned if it's not kept in good condition.