The Return of Zaros

Dawn of a new golden age
Start the quest by talking to Zaros in his restored throne room and he will bless you and your defence and attack will be doubled, then speak to Guthix and he will tell you to give him all four godswords and once you give them to him he will combine all of them together with his power creating the Balance Godsword.

Now head to Daemonheim to where the dragonkin statue is and Bilrach will be there waiting to fight you. Once you defeat Bilrach head back to Zaros and he will tell you to take out Lord Drakan and give you a silver stake and a hammer and teleports you to Lord Drakan's coffin. Open the coffin and use the silver stake on Lord Drakan and the player will start carving the stake into his heart.

Once you finished head back to Senntisten and there will be a Zarosian army fighting the armies of Saradomin and Zamorak with the help of Azzanadra and Nex. Head to the outpost and a Saradominist general and Zamorakian general will attack you but Robert the Strong will appear and help you fight them.

Once you've defeated them head back to the throne room and you will see a cutscene of Zaros and Guthix fighting Zamorak. Zaros will stab Zamorak with the Staff of Armadyl and Guthix will blast him and give his power to Zaros.

An angry level 135 Saradomin walks in and starts attacking you and he can only be harmed by the Balance Godsword. Bring cooked rocktails and equip your Balance Godsword. Once you've defeated Saradomin he will fade away and Guthix will take his staff.

There will be a cutscene in which Guthix goes back to sleep and a lot of happy people will gather around Zaros and thank him for saving them. The Wilderness will become a place with grass and trees again and Morytania will be restored to its former state and all the followers of Zaros will be brought back to life to live with him. A happy ending!

Rewards

 * You become invincible and immune to poison and all spells except for when you are in PvP.
 * 140 million coins
 * All degradable armour you wear doesn't degrade.
 * Ancient hymn which grants access to Ancient Blessings.
 * Full Torva set.