In the battle called the
Titanomachy Zeus freed his hideous cousins the
Cyclopes and the
Hecatonchieres who aided him in his battle against the
Titans - the latter as soldiers and the former by forging
Poseidon's
trident,
Zeus's
thunderbolts and
Hades'
helmet of
invisibility. After they were defeated, most of the Titans were sent to rot in
Tartarus.