Advanced #01 Super Size
Activate Megamorph and select your Giant Red Seasnake.
Activate Megamorph and select Harpie Lady.
Activate Megamorph and select Robotic Knight.
Switch to Battle Phase.
Attack opponent's Giant Red Seasnake with Harpie Lady.
Attack opponent's Celtic Guardian with your Giant Red Seasnake.
Attack opponent's Robotic Knight with Ryu-Kishin.