From Halopedia, the Halo wiki
Growing up, Silset 'Chava and his brother Oebrin 'Chava served as weaponsmiths for the Sangheili of the Covenant. The two optimized Covenant weapons for Sangheili use either on the battlefield or on hunting preserves, sometimes drawing the ire of any San'Shyuum that learned of the brothers' unsanctioned modifications, secretly giving both Sangheili suppressed satisfaction. At some point, Silset accepted a position at the Covenant Ministry of Preparation's Sacred Promissory, where he put his extensive knowledge and experience with Subanese blamite to use.
When the Great Schism began, both Silset and Oebrin 'Chava found themselves united under Thel 'Vadam's Swords of Sanghelios, having always wanted for the Sangheili to break free of the Covenant. As weaponsmiths of the Swords of Sanghelios, both brothers intended to use their mastery of weaponsmithing to new, more honorable ends. Together, the two modified a Type-57 carbine to take on the "role and the soul" of Suban and adapted key attributes of the Type-31 needle rifle, the favored weapon of Silset. The result was the "Blood of Suban", a carbine that fired Subanese blamite.