Discord would simply have played a game with his cousin while the others were regaining Luna's powers.
The games were from different games for Discord to finally persist, however, both Discord and Eris won the games while the others did not.
The last game was what caused the castle to crumble and since both Discord and Eris were temporarily without powers to compete well, they need to escape, reaching this stage where Eris prefers to die than accept that he is better than her in every way. She doesn't want to be ers cousin's shadow anymore.