There is a lot of symbyotic organisms - lichen, humans and their gastrointestinal microbiota, and so on.
For example, there is cold climate with some pathogen present in atmosphere of planet in your story.
One of symbiotic creatures in your story breathes away antidot against this pathogen, and this creature is small and docile. While other creature - is big and fluffy, and it carries the first one like breathing apparatus, constantly warming it in its hands and feeding it when it can. Without each other small breather creature and big fluffy one cannot exists. Big one will be poisoned by pathogen in atmosphere, small one will starve and freeze.
Or, for example, there is big, island size jellyfish like creature, slowly floating on surface on ocean. And there is full tribe of smaller rodent like creatures living on its surface. The rodents cannot swim, and they feed on parasites living in jellyfish.
If rodents stops eating jellyfish parasites, jellyfish dies and rodents drowns.
Also there can be symbiosis between big Mycelium, that pumps nutritional materials from deep underground, and forest above it. Mycelium cannot digest nutritional materials, but plants - can, so mycelium feeds plants, plants feeds animals, animals dies and mycelium devours animals corpses.
There is symbiosis between animals and plants. Plants makes O2 and edible matter from water, minerals, CO2 and animals by-products (manure and urine), while animals feeds on plants and spread plants seeds (for example, via eating fruit and dropping seeds around). Plants cannot live without animals, animals cannot leave without plants.
I think, if you read links i provided, you'll have lot of inspiration. But its all hard science, no telepathy, no magic...