Hyperion

Hyperion, called Bladebreaker, is a Grey Knight of the Eighth Brotherhood who was once the boy Zael and became the psyker who snapped Angron's Black Blade on Armageddon. He is not the planet Hyperion. The planet did not stand in Squad Castian while a Daemon Primarch ended the rest of the squad.

The First War for Armageddon made him a legend the Space Wolves actually respect. The Months of Shame made him a witness: he stood on Fenris while Grimnar killed Inquisitor Kysnaros aboard Corel's Hope, and then had to live with what the Inquisition had asked the 666th to do to the survivors.

Titan took him back. Recklessness had already barred him from the Augurium once. After Armageddon the Chapter found a use for a knight who could break a god's sword and still doubt the next order. He remains that use.