This is the edgiest name in the world, which is why I clicked the wikipedia page: Mind-Flaying Spiral Snails. They actually do have some pretty intense psychic effects on some other species, apparently. Their shells look like a vortex, according to what everyone says. I don't think I can safely see one in person, but they're cool to read about because they're incorporated into a bunch of cultural practices in the planet they're from. Apparently they're crazy invasive my dimension, though.

They're sophonts, so not exactly animals, but there's a badly threatened species called Eusophontarians that are at risk in my home dimension. They're pretty cool in the dimensions where they're still thriving. At least, sort of – they don't actually live inside the dimension, so much as cling to the outside like sharksuckers. Anyway, since they don't have material biology, they can get away with being fully modular. Those are awesome.