There's a genetics thing referred to as a chimera where a person's DNA doesn't match up to them like it should, often the result of something like twins fusing in the womb, but the mythological chimera doesn't exist.
I think, there are many spiritual beings and Chimera could be one of them.
I tried before years summonig Greece Sphinx, - in Greece mythology a sister of Chimera - and by my opinion is real. So, I think Chimera could be real spiritual beings too.
There's a god named Tutu (Kemet) who happens to be similar to a Chimera. He is often represented in the form of a sphinx with a snake for a tail, though he also appears with snakes/scorpions for paws amongst other things.
He essentially is a deity who ended up functioning as both the royal/kingly ka and the Nisut-bity (king/pharaoh) during the take over by Greece and Rome. Apparently at an earlier date there was a similar creature that represented the kingly ka, so as no one did the actions necessary to keep the universe going, he came forward as a sort of a savior.
On another note, I'm sure there are thoughtforms, servitors, and various beings running around that might look like a Chimera or could look like a Chimera if they wanted. After all, they aren't bound by the physical world like we are.