Instructions
Using the Portals
Put some distance between yourself and The Fallen. The Fallen will try to melee attack you.
Run to one of the area's four portals. Stay in front of it while The Fallen is recovering from his melee attack.
Fire at The Fallen to get his attention. He will turn toward you and launch a fireball attack.
Dodge the attack. If timed right, The Fallen's fireball will hit the portal and be reflected back at him through another portal. This will stun the Fallen. Run to him and melee attack while he's down.
Repeat the steps until a cut scene is triggered. The cut scene will show The Fallen warping to a higher part of the pyramid and Optimus will follow him.
The Final Showdown
Jump over the smash attack that The Fallen immediately uses and aim yourself towards him. When you land, immediately melee attack him twice and move quickly away. Repeat this attack pattern until the game gives you a series of Wii commands in a Quick Time Event.
Input the commands exactly as they appear on the screen until Optimus Prime punches The Fallen to the ground. Attack The Fallen twice with a melee attack while he's down. Move away as he prepares to use the ground smash again.
Repeat steps one and two. After five or six Quicktime Events, The Fallen will be defeated.