As each player's Life Points decrease, their respective normal counterpart will have more and more of his body wiped out. When a player loses, he will be sent to the Shadow Realm.
Marik's Turn
Summons Vampiric Leech (500/1200), whose effect allows it to attack Yugi directly (Yugi 3500)
Marik pays all 699 LP (Marik 1) and tributes his other monsters to activate Ra's effect (6899/5399)
Yugi activates Soul Taker, increasing Marik's LP (Marik 1001) and tributing one of Marik's monsters. He tributes Egyptian God Slime. Since it was made of two monsters, he can use it as a double Tribute, which is needed for Obelisk's effect (3899/2399)
Marik pays 1000 LP (Marik 1) to activate Ra's effect (4899/3399)
Activates Class System, protecting Ra from Obelisk's effect