The Great Brain Robbery

Bank/dismiss any pets or familiars.

Upon arrival on Harmony Island, go through the dialogue, or Brother Tranquillity will teleport you back to Mos Le'Harmless.

Run outside and head slightly north to the statue. Pull the statue, then climb-down statue.

Equip your diving gear and descend the stairs.

Run past the zombie pirates.

Repair the stairs at the end of the tunnel, then climb them.

If you happened to bring your planks in a plank box, be sure to remove them so you can repair the stairs.

Climb the ladder.

Peer-through the peephole on the wall.

Make your way back to Brother Tranquillity on Harmony Island and speak with him.

Travel to the Edgeville Monastery.

Search the southern bookcase on the ground floor of the western wing to find a prayer book.

Read the book.

Head back to Brother Tranquillity who teleports you to Harmony Island.

Wear your holy symbol and choose the option Recite-prayer on the prayer book.

Talk to Brother Tranquillity.

Travel to Fenkenstrain's Castle, which is directly north-east of the Canifis lodestone.

Go up on the staircase in the north-western corner.

Go up on the northern ladder behind the jail gate in the centre.

Talk to Dr Fenkenstrain.

Equip your ring of charos and talk to Rufus in the Canifis meat store.

Speak with Rufus again after the cutscene if you did not receive a wolf whistle and crate parts.

Start crafting on a clockmaker's bench in a player-owned house to make 10 wooden cats with 10 planks and 10 bear fur. You can also buy them off the Grand Exchange.

Travel back to Dr Fenkenstrain with all of the required items.

Build the crate on the hotspot, east of the ladder.

Add-bottom to the crate.

Fill the crate with the wooden cats.

Take off your fishbowl helmet and Blow the wolf whistle to call Rufus.

Use the shipping order on the crate.

Travel back to Mos Le'Harmless.

You can buy a hammer and a tinderbox from the Trader Crewmember (located south-west on the dock).

Speak with Brother Tranquillity to get back on Harmony Island. (Brother Tranquillity now also has a "transport" option available to players)

Climb down the ladder and talk to Dr Fenkenstrain.

If he is not there, exit to lobby and join the world again.

Return up the ladder.

Equip your diving suit and head north to the ship that has run aground.

If you walk outside without diving suit, you will be teleported back.

Equip your weapons in preparation for fighting enemies, otherwise you will have to return to the windmill to do so. Attempting to do so outside will give the message: "You cannot wear that without the gas affecting you."

Open and then search the locker on the west end of the ground floor to get a fuse.

Climb the ladder and take a keg of powder found next to a cannon.

Grab the tinderbox from the front (east side) of the ship if you have not brought your own.

Go to the front door of the monastery (the main building on Harmony Island).

Use the keg on the door.

Use the fuse on the door.

Use your tinderbox on the fuse.

Pass the door to enter the monastery.

Kill some sorebones until you get the following items (the items drop one at a time and the next item won't spawn until the current one is picked up):

3 bell jars

A pair of brain tongs

A cranial clamp

30 skull staples

Talk to Dr Fenkenstrain downstairs in the mill. Make sure to give him a hammer or you will be stuck.

After the cutscene, go upstairs and talk to Brother Tranquillity.

Pass the door of the monastery and confront Mi-Gor.

Kill Barrelchest.

Take the Barrelchest anchor.

Return to Brother Tranquillity.

Quest complete!