Oblivion

Speak to Sir Siron and ask him about the shrine of the Dragonslayers and how you want to destroy the curses of the Barrows Brothers.

Now you must kill all the Barrows curses and open the chest at the end to get the reward and a symbol of the Dragonslayers.

Now go back to Siron and show him the symbol, he will then make a key out of it then tell you to make your way to the Dragonslayers cult shrine.

Go north-west of the Barrows site until you see a fence with a hill. Go onto the hill and use your spade to get inside. Then you will need to use the key on the coffin to unlock a Dragonslayer curse (lvl 98).

Now kill it and take its Cult Key. Then use it on the Ancient Door in the room.

Now you are in the Cursed Cult and you will need to try and lift the curse. Speak with Siron in there and he will then kill a lvl 300 curse on his own and then he will say we need to kill the lord.

Follow him as he runs into the room north labelled: Room of Zamorak.

Enter then there would be a cutscene of a lvl 450 curse attacking Siron. You will now need to help him to kill it by taking a Shadow Sabre, then attacking the curse until dies dead.

Congratulations, quest completed!

Reward

 * 4x 100,000 experience lamps
 * 1x 300,000 experience jar
 * Access to the Barrows Dragonslayer cult rooms
 * Access to wear Dragonite equipment.
 * 425,000 coins
 * Torag's helm
 * Guthan's warspear
 * Verac's brassard
 * Karil's coif
 * Dharok's platelegs
 * Ahrim's hood
 * A random barrows item.
 * Ability to receive Barrows defender as a lucky drop from any Barrows brother