Father Renaldo is Father Enrico Maxwell's second-in-command of Section XIII, Iscariot Organization. He was the one who had informed Paladin Alexander Anderson of a vampire attack in Badrick, Northern Ireland... and of the Hellsing Organization's involvement in containing the attack. Like all members of Iscariot, Renaldo is fanatically devoted to the Catholic Church... and of Iscariot's holy mission.

(Source: Absolute Anime)