The everlasting mercy of Riou's Bright Shield rune fades to nothing when it's placed in competition with something. Normally it's the Black Sword Rune, the opposite half of the Rune of Beginning that compels it's user to fight no matter what. The DL arena is special, though- both Jowy and Riou are at peace with their runes here and are able to control it, meaning the full weight of one half of a rune able to grant eternal life or everlasting mercy can be brought to bear on the enemies of the Dunan Republic's founder.
The display of power was put to use instantly in Riou's first fight in Heavy, as Forgiver Sign reduced Ershin to scrap metal, giving the robot an 0-1 record and the dubious honor of being unable to even land a single attack in his debut Heavy battle.
