Dante can't allow his own flesh and blood to rule over the people he had just freed, and Vergil can't let his brother obstruct his bid for domination. With the two brother's at odds, they cross swords. As the two Nephilim battled, Dante continually pleaded with his brother to reconsider, to no avail. In the end, Dante had no choice but to unleash the devil inside him and run Vergil through the heart with Rebellion. Unsure of what to do, Dante forced Vergil to the ground, impaling him with his sword until Kat begged him to let him live. Sheathing his sword, Dante helps Vergil to his feet, and declares that the world is under his protection. Vergil responds that his brother has chosen the wrong side, and that he'll never be human. Opening a dimensional rift with Yamato, Vergil mutters "I loved you, brother" before disappearing through the portal.
Just after you have received the devil trigger, you will enter a building and battle against some Rages. To get the key, you will need to launch an enemy into the air and then use your grapple to launch off them and jump up to the balcony above. Once you get to the balcony, you can find the key in the corner. 2b1af7f3a8