Aquaman

In a story set in the past, after the death of his father, Arthur Curry takes to the sea to search for his mother and Atlantis.

Aquaman investigates a deep trench with the Sea Devils, until a monster arrives and takes Deep Blue down into it. Aquaman descends, and finds his old foe, Black Manta.

Mera, insane with grief over the loss of her baby, attacks Aquaman. She is apparently killed.

Aquaman returns to Atlantis to find it destroyed by the Spectre and many of his former subjects dead. He leads the survivors to Sub Diego but their assimilation will not be easy.

Manta convinces several Tritonians to join him in attacking Poseidonis, forcing Aquaman back to reality. Aquaman joins the fight and (possibly kills Manta).

Aquaman leads his people from the shattered city, and goes to Tritonis, only to discover that Tritonis has been completely destroyed. He and Tempest lead the armies of Atlantis...