Why did Zeus try to kill Bianca Di Angelo and her brother?

The gist of this is that a child of the Big Three (Zeus, Poseidon, Hades) will make it to 16, and then either save the gods or destroy the gods. After WW2, the Big Three swore a pact to have no more children because of this prophecy. However, Hades had two living children during the war: Bianca and Nico Di Angelo. read more

Hades was the first one to break the prophecy by siring Nico and Bianca Di Angelo, and that freaked the crap out of Zeus. He wasn’t very fond of the idea of Olympus being razed, so he decided to kill the siblings before the prophecy ever came into fruition. read more

Bianca di Angelo was a Greek demigod, a daughter of Hades and the mortal Maria di Angelo. She was the older sister of Nico di Angelo. She became a Hunter of Artemis after being saved along with Percy Jackson, Grover Underwood, Thalia Grace, and her brother Nico by the Hunters. read more

Because of the Great Prophecy. So as we all know, the prophecy was a prediction made by the Oracle of Delphi that foretold the rise or fall of Olympus by a child of the Big Three. read more