In this mission, you have to kill all of the enemies riding in a "wagon" before they escape.
This one can be found in a crystal puzzle in Vestibule in Mission 13. It's in the ledge at the left of the corridor, portrayed as a bull with red shining eyes.
- You should skip this Secret Mission, then come back and play it in the Heaven or Hell Mode. Obviously, you should just shoot the Hell Wraths, as the explosions will immediately kill the Hell Lusts.