The Blood Purge (血の粛清 Chi no Shukusei?) is an event in Tales of Symphonia: Dawn of the New World that took place half a year prior to the events of the main plot in the city of Palmacosta, once the largest city in Sylvarant prior to its destruction in Tales of Symphonia.
The Blood Purge was allegedly carried out by Lloyd Irving, who indiscriminately slaughtered the innocent citizens of Palmacosta, as they supported the Vanguard instead of the Church of Martel. This largely tarnished Lloyd's reputation as a hero, though some still held him in high regard. Emil Castagnier's parents, Lana and Reysol, are notably murdered during the tragic event, which is viewed from his perspective as they flee to the port prior to their demise. Marta Lualdi is shown attempting to flee the city during the onslaught, escaping with Ratatosk's core, before being surrounded by Vanguard soldiers.
Marta beckons for Ratatosk's aid and it greeted by a bright light that knocks her unconsciously onto the ground, the emblem of Ratatosk etched onto her forehead. When she awakens, she finds the soldiers incapacitated on the ground and between them Emil, who she believes saved her. Emil then leaves to find his parents, finding Lana still alive as she tells him to go to his aunt Flora in Luin before dying. From this point forward, Emil holds a deep grudge for Lloyd for murdering his parents.
Later in the story, the actuality of the event comes to light, revealing that the "Lloyd" who attacked the city was in fact not the real Lloyd Irving, but Decus, who was to attack the Vanguard's base as Lloyd in order to tarnish his reputation. He transformed himself into a Lloyd Centurions nucleus and committed crimes in his name to drive people further away from the Church of Martel's influence and seek refuge instead in the Vanguard, which seeks to revive the Sylvarant Dynasty. The plan also aimed to rid of Vanguard members who opposed Commander Brute Lualdi's plans. In addition, the emblem that appears on Marta's forehead is fake, the real kernel taking the form of Aster Laker, who bears an identical resemblance to Emil. Aster, a shell created by Ratatosk without consciousness, develops the consciousness of Emil when he meets Emil's mother, Lana, and is recognized by her. The fate of the real Emil is unknown, but it likely that he too fell victim to Decus rather than escaping.