Ken Griffin of Citadel in a letter to clients on Friday addressed for the first time the firm's purchase of assets from Leopold Aschenbrenner's Situational Awareness hedge fund. 

According to a letter obtained by CNBC's Sara Eisen, Griffin told clients that Citadel has unwound more than 80% of the aggregate risk from the original portfolio purchased by conducting more than 100 block trades over $4 billion in market value.