Activating this secret mission is a pain, as you only get one shot at it. If you fail to trigger it, or you fail to meet the objective, you'll have to reload from your last save point to try again. But you're up for the challenge, right, Devil Hunter?
In Mission 17, you should start at the far end of the Broken Bridge. Instead of jumping through the portal, make your way back to the Cathedral where you first encountered Phantom. If you fall into the water, you will not trigger the mission. If you have trouble jumping across, you can always use Air Raid with Alastor. When you land on the far side, the mission should trigger.
- Avoid the Death's attacks and utilize the Jump Pads he scatters for you. This takes patience and luck, and some resetting, as he scatters the pads randomly and you will more than likely end up in the drink a few times.
- Kill the Death, jump on the arch above the door to the cathedral, and use Air Raid to get to the blue orb fragment halfway across the bridge.
- Once the secret mission starts assuming you used Air Raid to cross the broken bridge use a Devil Star fight Death utilize the Jump Pads and aim as high as possible activate Air Raid and head to the Blue Orb ignoring Death once you have the Blue Orb finish him off deafeating him will charge your DT use Air Raid a third time to cross the bridge back.