This mission is found during Mission 16, in the Fortuna Castle Gate area. To reach it, from the area where you fight the Basilisk, go halfway up the path to the top of the area (the bottom of the unbroken staircase), and there will be a wall with red orbs next to it. This mission can also be reached by backtracking from the beginning of Mission 17, bypassing the combat from the previous mission.
To reach the ledge, use Devil Trigger and the Wall Jump/Air Hike combination and on top of the ledge you will find the Secret Mission. For Nero you must use EX High Roller (3 charge) then Wall Jump/Air Hike in the same place during Mission 3 (though you need to backtrack a bit).
There are two statues on each side that need to be destroyed. You need to aim horizontally at the statue first before doing anything, since PF398: Revenge can only be adjusted vertically. You also need to get a little bit closer to them so you can aim easily (you can check which way Dante is facing by pressing the Right Joystick). Once you are already aimed at the statue only then will you use PF398: Revenge, which doesn't need to be charged.
In other words:
- Go a little closer to the target.
- Check your aim by pressing the Right Joystick.
- Once you are aimed, execute PF398: Revenge (no charging is needed).
- Repeat the above steps for the other statue.
Note that little means a distance wherein you are efficient at aiming. For the first statue, you have to move to the edge of the platform, otherwise you will shoot the floor with Pandora when you aim down.
An almost foolproof method to aim Pandora straight is to, when you first enter the Secret Mission area, DO NOT MOVE. Press R3 (the right joystick) to center the camera behind you. You will be facing the first statue, the one at the bottom of the stairs. Run STRAIGHT forward by pressing ONLY forward on the left joystick, not moving the camera. At the top of the stairs, pull out Pandora, change it to Revenge, and aim for the base of the far away arch--the one Nero passes under when he first arrives at the headquarters. The statue is THAT far away. You will need to move the camera slightly to one side or the other in order to view the laser-sight that Pandora gives you. Once you're aimed, fire, and you should hit it. Now all you need to do is walk STRAIGHT backwards. The camera doesn't like facing Dante, though, so the best thing to do is to center the camera behind you again, tap straight back on the joystick to spin Dante 180 degrees, then center the camera with the right joystick yet again. Run to the other end of the platform, down the small set of stairs, and use Revenge again.
- Using this method, aiming the second time is much more difficult. (Sometimes Pandora will shoot right between the statue's legs.) If you're quick with destroying the first statue, and want to save yourself the hassle of unpacking Revenge, you should have plenty of time to run to the 2nd one and simply shoot it with Ebony and Ivory.
While this mission was designed for Pandora, there are a couple strategies that allow for completion without it. The first way is to use Ebony and Ivory. The statues are extremely brittle and even one bullet will destroy them. Simply run down the stairs, take about 4-6 steps from their base towards the first statue, jump, and fire. If you ran straight, your aim should be just right to hit the statue. Turn around and run back towards the other statue. A few steps past the doorway, jump and fire again.
Another way of completing this mission is with Rebellion, have the Swordsmaster style at level 3 and use Quick Drive] When the mission starts, walk towards the statue on the left. When you exit the small building check your aim and use a Quick Drive. It's much faster than having to change Pandora from PF013: Epidemic all the way to PF398:Revenge. When you've destroyed the first statue, Devil Trigger and run towards the bottom of the stairs and go a little further and then use another Quick Drive and destroy the statue. If done correctly, this should leave you with roughly 8 to 12 second left on the timer.
Yet another method also exists when using Round Trip and Coyote-A or Quick Drive. When the mission starts, charge up round trip and move to the base of the stairs and release Round Trip and run to the other statue while Rebellion is returning to you. By the time you are close enough to the other statue just shoot it with Coyote-A or use a Quick Drive and it will be destroyed leaving you with about 1-3 seconds on the timer so you have to be quick.
For Nero your only way to break the statues in time is to use Maximum Bet, so you will need a lot of Devil Trigger, and even then it's very easy to screw up and you will only have one shot at this.