Complex sentence: Grover finally finds Pan, but the god of the wild is dying and wants Grover to tell the other satyrs that they must save the natural world themselves, his spirit passes into all present, Grover in particular, when he dies.
Split into simpler sentences: Grover finally finds Pan, but the god of the wild is dying and wants Grover to tell the other satyrs that they must save the natural world themselves. His spirit passes into all present, Grover in particular, when he dies.