ancient Greek mythological giants with 50 heads and 100 arms

The Hekatonkheires (Greek:  Ἑκατόγχειρες - "Hundred-handed ones") are one of the three races of beings born to Ouranos and Gaia, the primordial gods of the sky and the Earth. Their names are Kottos (Greek: Κόττος), Briareos (Greek: Βριάρεως) and Gyges (Greek: Γύγης).

Titans collapse under the boulders thrown by the Hekatonkheires ('The Fall of the Titans by Peter Paul Rubens, 1637–1638)

The Hekatonkheires received their name because they each have a hundred arms, fifty on each side of their bodies. Despised by their father, the Hekatonkheires were thrown into Tartarus alongside their brothers, the Elder Cyclopes, guarded by the monster Kampê. Many years later, Zeus, alongside his brothers and sisters, freed the Hekatonkheires and the Elder Cyclopes from their prison so that they might help them in their war against the Titans. During the war, the Hekatonkheires threw rocks at Mount Othrys, the Titans' base, reducing the mountain to half its original size. After the Titanomachy, the Titans were cast into Tartarus, and Zeus appointed the Hekatonkheires to be their jailers.