Guthix's Altar

Starting and during the quest
To start the quest, all you have to do is talk to Duke Horacio and ask him for full Guthix (only if don't have any of the set), an anti-dragonfire shield, and a dragon-stun battleaxe. After all the talk with the Duke, go to the back side of the castle, you will find a faint Guthix symbol on the castle and a hole that is the shape of the Guthix symbol. After going down, you will have to go along the trail then go up when you go up the second pathway up north. When you see a portal and go port with it, you will end up in a maze. Once you're in the maze, you will have to got to the end of the maze. Then there will be a portal. go in the portal. Then, you will be at the door to Guthix's altar. Once you go in, you will have to fight the Guthix dragon until you die or stun it. If you try to go back, the door will be locked.

Ending of the Quest
You don't kill the Guthix dragon, when all of his life points are down, he will get dizzy and drop 13 green dragonhides and dragon bones. Then, get to the treasure chest behind the altar and get the Amulet of Life. It takes 15 minutes for the Guthix dragon will snap out of being dizzy, so don't examine the Amulet too long. There will be a tunnel left of the chest, go into it and you'll find yourself in Varrock. To get to Lumbridge more faster, do the Lumbridge home teleport. When you get to the Lumbridge Castle, give the Amulet to Duke Horacio in order to complete the quest.

Rewards

 * Access to the Underground Pass of Lumbridge
 * All the Guthix armor
 * Dragon-stun battleaxe
 * Anti-dragonfire shield
 * 130,000 coins
 * Dragon-stun battleaxe
 * Anti-dragonfire shield
 * 130,000 coins