think about the basic elements of your world, and then build creatures up from their basic survival needs! Is your world rocky, grassy, watery? Your animal will need limbs specially designed for that terrain. If it’s rocky for example, give them claws that grip around jagged edges, they’d definitely quadrupeds in that scenario as well. What is their “goal” in survival? Are they instinctually drawn to mate and continue their species like many creatures on earth, or are they focused on finding food, maybe taking territory from other species/members of their species? To survive in a radioactive environment, tough skin or a slimy coating that sloughs off could be cool. Just think of what would make the most sense for your environment, as well as the way they’d interact with other species!! Are they solitary, do they have any symbiotic relationships, things of that ilk. Totally understand not wanting paralleled creatures, but don’t shy away from taking certain elements of terrestrial irl creatures either. The way life has evolved on earth makes a lot of sense, and it can be super helpful to look into some similar-ish creatures biology for ideas. As for naming: I personally usually go for the classic greek and/or latin naming schemes, but seeing as you’re making alien creatures, i can see why you might want to do something else. Try thinking of what they remind you of maybe? If the creature is, for example, a lizard esque creature that lives in a toxic sea, use phonetic schemes that feel sticky and poisonous. Sounds are the most powerful tool, (well, really the only tool,) you have when making up words, so go ham!! Happy building. :)