When Ruby Rose sees Emerald Sustrai in the audience of Amity Colosseum, despite her supposedly having returned to Mistral the day before, she becomes suspicious and leaves to investigate. However, in the maintenance hallway behind the spectator stands, Ruby runs into Mercury Black, who is walking perfectly fine despite his alleged leg injury inflicted by Yang Xiao Long in a previous fight.
When Mercury acts suspiciously, Ruby reaches for Crescent Rose, but realizes she did not bring it with her. At that moment, the next Vytal Festival match is announced – Penny Polendina vs. Pyrrha Nikos. Mercury comments that the match of magnetism and metal can only end badly.
Unarmed and alone, Ruby decides to escape rather than fight Mercury. When she first tries to simply side-step him, he matches her movements and prevents her from leaving. Ruby then attempts to fly past him using her speed Semblance, but he manages to intercept her with a kick to the chest. Ruby falls to the ground winded and reaches for her Scroll to call for help. However, Mercury blasts it out of her hand with a shot from his boots and moves in to attack Ruby with a flurry of kicks. Ruby is able to successfully dodge Mercury's blows, and seeing an exit, manages to bypass Mercury and speeds off with her Semblance.
However, she returns to the stands too late to make a difference in Pyrrha and Penny's match, for Penny has already been destroyed by Pyrrha's Semblance due to Emerald's interference.