World backyard --> Great outcast ref; he is not tied to any one place
Held by Earthly bonds --> I really like this, perhaps because Bellona mentioned it in their thread together? c:
Your not a specific thing --> Great hybrid ref. Immediately thought this was for a hybrid.
Seem to be everything --> I fail this, but only because he cannot be everything. Hybrids are a mix of two animals only, which is hardly everything.
Title is a great clue. Also thought it was a hybrid.