Behind the castle is a ladder that RS gold leads underground. Go down it and you will find 3 paths. Take the trail in the center and you're going to discover a large open area with a bunch of level 250 demons. Kill one of them and it'll drop its mind. Use the head with some cloth (you want 10) and cover it with a needle and string. Get a team from Zaff or a different player and use it with the head to turn it into a head on a pole.

Being it to Willus and the monster is going to be completed. Obviously such monster's do not only come to life. Willus will give you a letter to bring to Merlin requesting that he will help to bring the monster to life. Merlin doesn't want to support the monster, therefore bribe him with 50gp. He gives you a few Magical Essence and tells you that it can be smithed to a heart. Use it with an anvil to Find a Magical Heart. (gives 500 Smithing experience)

Bring the guts to Willus to complete the monster. Now a cutscene will play and the creature will break down a castle wall and also dip into the sea where you can't access to it. Yet. Talk to Willus and he'll tell you about a magical armor known as"Merma Armor" that allows one to breathe underwater.

The substance to make it is a rare ore which may only be found submerged. Get your swimming equipment and have Murphy bring you underwater. Close to the crabs is a crack in the rock that you can go via (50 Agility required) for an underwater mine which has the ore you need. Mine about 25 of them and head back to Willus. He gives you a Magical Chisel. There are three pieces: the Merma Top, the Merma Leggings along with the Merma Mask. You need 60 Defence to utilize it.

Speak to Willus and inform him that you have the armor and he will provide you a special publication. Equip the armor and leap in the water in which the creature went. Now you are underwater and the monster is right in front of you. He's level 200 and uses melee strikes and an occasional magical strike.

He can hit at the 40's but these strikes are rare, and a frequent hit is about 10 or even 15. You can use lobsters but swordfish are greatest here. Make certain to bring Prayer Potions, too. When you have him 10 hitpoints use the publication that Willus gave you on him to cast a spell that will finish him off. After he is defeated he'll fall Magical Bones. Take these to cheap OSRS gold Willus to demonstrate that you defeated the monster. Now speak to King Vargas and decide to inform him what happened. Fortunately Willus has already told him everything. Congratulations, quest complete.