Regicide

Talk to King Lathas in Ardougne Castle. Dialogue: I assume you have a plan? → Yes.

Note: You can start this quest by talking to King Lathas directly after the completion of Underground Pass.

Travel through the Underground Pass, entering on the far west side of West Ardougne. Refer to Underground Pass/Quick guide if you become stuck.

Search the abandoned equipment next to the fire for the cloth. Use the cloth on your arrows, light them, and use your bow and lit arrows to open the gate.

Take a plank to the north, if you did not bring one. Head south, then east, crossing the gap with a rope while ignoring the water.

Cross the grid using the same pattern you did before. Pull the lever.

Search the odd markings to bypass traps, then go directly down the well. You do not need to re-collect the four orbs of light for the furnace.

Dig the loose dirt in the first southern cage, cross the ledge, and take the swamp shortcut (with 50 Thieving) or traverse the maze.

Go south and squeeze through the pipe, pass through the tunnel, and head north-east where the paladins were.

Use a plank on the flat rocks. Open the doors. Optional: Charge your Iban's staff or Iban's staff (u) at the Flames of zamorak well just before entering the large area with Iban's Temple, if you brought either one.

Travel south to Iban's Temple and enter the well (optional: talk to Koftik for some free food).

Exit the cave to the west.

Run west through the forest, then talk to Idris when he spawns (this may take a little while).

Follow the map to Lord Iorwerth.

Run south-west, jump the leaves trap (click the middle square closest to you).

Run west, pass through the sticks trap. (For this stick trap, and any stick traps you may encounter during this quest, simply stand one square in front of the trap and spam-click the trap until your character moves over it. This will negate all damage from the trap.)

Follow the path north-west, jump the leaves trap, and continue north until you reach the Iorwerth Camp. Cross the Log Balance to reach it.

Talk to Lord Iorwerth.

Follow the map to the Elf Tracker.

Run back the way you came and run south-east once you reach the Sticks trap (do not go through the sticks trap).

Talk to the Elf Tracker.

Talk to Lord Iorwerth again. (You must have an open space in your inventory to receive the Crystal Pendant.)

Talk to the Elf Tracker again.

Click to follow the tracks, they are west of the tracker, at the north-west corner of the blue mushrooms.

Climb through the dense forest, kill the Level 110 Tyras Guard that immediately spawns.

The guard can be safespotted by the mushrooms to the south-west.

Go north, pass tripwire and go through more dense forest.

Run west then south through more dense forest, talk to General Hining in the camp.

Take at least 2 barrels. 3 is highly recommended in case you fail distillation of coal tar in upcoming steps. The second barrel is needed for Mourning's End Part I.

Go back to the Elf Tracker and use 2-3 of your barrels on the tar just south of him to obtain barrel of coal tar.

Get a piece of sulphur from right next to where you got the tar.

Talk to Lord Iorwerth with one empty inventory slot. Players wishing to keep their Crystal pendant should drop it each time before talking to Lord Iorwerth (or King Lathas) for the rest of the quest. Banking it will not keep it safe!

Read the book and keep it in your inventory.

Talk to Lord Iorwerth about each item (sulphur, naptha, quicklime, barrel, and fuse). Dialogue: I need some quicklime. → I need some sulphur. → I need some naphtha. → I need a barrel. → I need a fuse. → That's all thanks.

If you don't have a pot grab one from the spawn north of Lord Iorwerth.

If you need limestone, make sure you have your pickaxe. Head east through the Dense forest, jump over the leaves, then into the mine. Beware of Level 88 dire wolves.

Go back to where you got the barrels so you can use the small furnace, or teleport to a bank near a furnace (Falador, Edgeville, etc)

Use limestone on any furnace (make sure gloves are equipped or you will take damage.)

With a pot in your inventory, use your pestle and mortar on the quicklime. If you do this incorrectly, you will need to repeat the previous step with a new limestone.

Use your pestle and mortar on the sulphur.

If you have not already created a strip of cloth, use four balls of wool on the loom in the farm south of Falador or near the house portal in the Hosidius area to make one.

The coal from your bank can be noted, but you will need to un-note it using Phials in the nearby general store once you get there.

Talk to the chemist Dialogue: Your quest. in Rimmington. Make sure you have the book in your inventory. (If you don't, the Quest Journal will not update!)

Un-note your coal and then use your barrel of coal tar on the fractionalising still outside. All 20 coal should be in the inventory at once, as leaving the interface for the still will reset all process towards making the naphtha.

Read this whole section first before you distill! When you are ready, operate the still:

Turn the tar valve on the right side all the way to the right (third marker).

Wait for the pressure gauge to land in the green zone, then turn the pressure valve on the left to the middle to halt the pressure. If it lands in the red zone, turn the valve right to relieve some pressure, then back to the middle.

Do not touch the valves again. Ignore the pressure gauge.

Slowly add 2 coal, then 1 additional coal whenever the heat gauge falls too low (well outside the green zone). The tar will still distill if the gauge is near the green zone (but not in it). Do not add 4 at once, it is likely to overheat and you will have to start again. A "pop" sound and the valves resetting does not mean you've lost the barrel of coal tar; simply restart from the beginning of the steps without exiting the interface. The process is fast and may use only 4-5 coal. If you forgot or ran out of coal, you can leave and come back.

Once the green bar is full you may exit out of the interface and automatically receive the barrel of naphtha

Make a second barrel of naphtha for Mourning's End Part I. No sulphur or quicklime needed to be added to the second barrel.

Use the pot of quicklime and ground sulphur on the barrel of naphtha to make a barrel bomb (unfused).

Use the strip of cloth on the barrel bomb (unfused) to make a barrel bomb.

Go through the Underground Pass once more. Bringing summer pies this time is highly recommended because you are now carrying a very heavy barrel bomb.

If you did not bring your own cooked rabbit, kill one north-west of the Elf Tracker and cook it. If you forgot an axe, there is a fire in the Iorwerth Camp.

Head to the catapult, north of the Tyras Camp.

If you did not bring a tinderbox, go south to Quartermaster's general store and purchase a tinderbox before you give the guard near the catapult the cooked rabbit.

Use the cooked rabbit on the guard near the catapult.

Use the bomb on the catapult.

Talk to Lord Iorwerth.

Attempt to enter Ardougne Castle.

Talk to King Lathas.

Congratulations, quest complete!