This is a series that I think is pretty old but not sure. It starts with a guy on Earth and a UFO lands. A lady falls out obviously in pain and a tiger/lion creature also falls out. They are being attacked by the quintessential gray aliens with a mind or sound weapon called the scree. Humans are immune to it. He helps to save them. They go off to fight the aliens and he meets many different kinds of races etc. The lion creatures are the best protectors in the universe. There is also a tree like race that are super smart and build and end up building all the tech for their war.