Complex sentence: The cast of the Outsiders was notable for having mostly new characters (Geo-Force, Katana, Halo, and Looker), two characters who refused membership in the Justice League (Black Lightning and Metamorpho), and a former Leaguer, Batman.
Split into simpler sentences: The cast of the Outsiders was notable for having mostly new characters (Geo-Force, Katana, Halo, and Looker). The other members were two characters who refused membership in the Justice League (Black Lightning and Metamorpho), and a former Leaguer, Batman.