For Poseidon; The God of Oceans and Seas, Earthquakes, and Horses, to die, people must no longer acknowledge these bodies. This angers Hades who asks Zeus to kill him. Zeus kills him with his thunderbolt.

Why did Kratos kill Poseidon?

Poseidon then made a desperate attempt to escape and survive, but is unable to reach the edge and is grabbed by Kratos, who then proceeds to crush his eyes and finally break his neck, killing the sea god once and for all. ... Even though Poseidon fought alongside his brother, he alone still had misgivings about Zeus.

What happened to the god Poseidon?

After being born, Poseidon was swallowed by his father Cronus because of a prophesy that said Cronus' children would someday overthrow him. Poseidon was eventually saved by his younger brother Zeus. Poseidon and his brothers, Zeus and Hades, went to battle with the Titans.