A Balanced Party
Start to speaking to Commodore Tyr in the Void Knights' Outpost. He will be having a conversation with Captain Korasi. You will interrupt, and Tyr will tell you both the Temple Knights and Void Knights are drawing a blank as to where the pest is.
He will ask for your assistance, and propose that you take Korasi and Jessika to the mainlaind to track it down. He will tell you that most of the Temple Knights were called back to Falador due to something unknown affecting the city.
Ask him where you should start, and he will suggest Port Sarim. Speak to Korasi, then head to Port Sarim. They will be west of the Squire that takes you to and from the Void Knights' Outpost.
Talk to Korasi, and she will suggest starting with the dock workers. Head slightly north and talk to Captain Tobias. He hasn't seen anything, but suggests Gerrant in the fishing store to the west/north-west might have.
Tell him you're tracking an escaped animal. A purple trail will appear outside of the shop. Follow the trail as seen on the map below. The purple indicated the path, and the red dots indicate places to search.
The Rusty Anchor
Check the mound on the north side of the Rusty Anchor bar. Return to Korasi. She will tell you to talk to the owner of the Rusty Anchor, and they'll meet you there. Talk to the Bar tender, and he won't be feeling well. He'll tell you to go ahead and search the basement, but he lost the key somewhere in the bar.
Search the junk pile on the ground in the north-east corner of the bar to get the key, then enter the basement from the north-west corner of the bar. Korasi and Jessika will follow you down.
Inspect the suspicious wall next to where Jessika is standing. You will use your pickaxe to knock a hole in the wall, and purple goo will start to flow out. She'll want a sample of the goo, and asks that you get an empty barrel from the nearby storage room.
Korasi will give you a Void Knight whistle in case you mess up. Follow the below pictures to get the barrel out.
Exit the door you came in, and they'll have the barrel filled with the goo. Kurasi will ask you to make up a story for the pub owner, and they'll meet you back at the ship. You can either lie or tell him the truth. Head back to Kurasi and Jessika - they are back where they were earlier in the quest.
You three will decide that the best went to Musa Point. Head to Musa Point, and talk to Korasi at the end of the docks. She suggests starting with the Bartender, Zambo. Ask him if he's seen anything odd lately.
He will tell you the storekeeper saw a "scorpion or something" nearby, and has recently become ill. He will ask you to fix his wall. Take the tools from the table in the south-west corner of the building.
Make sure you get a plank, log, chisel, and hammer. Inspect the shop wall in the north-west corner of the shop. Use a chisel on the log or plank to get a jointed log and jointed plank. Use them on each other to make a joist. Use the joist on the shop wall.
He will then lead you to where he last saw the creature. Follow the tracks as like before, using the map below.
Check the mound along the fence. You will notice someone has beaten you to it. Kurasi and Jessika will want to figure out more about the goo, and ask you to look more around the mound.
Investigate the mound again to find broken shards of waxwood. They'll then suggest going to the chemist in Rimmington, and seeing Rommik in Rimmington about the waxwood.
Start by talking to Rommik in his crafting shop about waxwood. He will tell you about recently doing an order for someone who needed a lot of waxwood boxes around Falador.
Head into the building west of Rommik, the Chemists' house. Korasi and Jessika will be on the east side of the house. Talk to the Chemist and start analyzing it.
You'll need to keep the heat, power stable, and the chemical sample in an appropriate state while the chemist works. The central vat shows what the current state of the sample is.
Add a sample to the hopper to mix it in with the chemical already present, and attempt to form the required state. If the heat is too low, stoke the furnace. Too high, open the vent. Same with the power - wind it up if too low, and use the break if it's too high.
You have to constantly watch the power and heat - adjust it accordingly. The table on the left will show you the current status of the power, heat, and what the compound needs to be. The table on the right shows you what mixtures of what makes what.
After the process reaches 100%, talk to Kurasi again. Jessika will offer to teleport you to Falador Park.
Talk to Sir Tiffy in the Park. You will catch each other up on the situation. Sir Tiffy will tell you that an Ali for the Kharidian desert showed up and is selling oak boxes. People in the area also started getting sick like the bartender and shop keeper.
Sir Tiffy comments that his accent is clearly fake. Sir Tiffy asks you to talk to him, or at the least get a box off of him. Head out of the park, and look just south of the east bank. Ask him why you would want a box, and he'll tell you that they have a complex puzzle lock on them.
If you manage to open it, you'll get a special prize. Have him tell you more about it. Buy a box off of him. Attempt to do the puzzle, then return to Sir Tiffy. Sir Tiffy will attempt it too, but doesn't get anywhere.
Jessika and Kurasi will have a try, but aren't successful. Use any combination of what you think you should do, but Korasi will take it and smash it open. It is filled with pest goo. Sir Tiffy asks you to talk to Ali again.
He won't tell you anything, so go back to Sir Tiffy. He suggests talking to Sir Amik to get some leverage on Ali. Sir Amik is in the White Knights' Castle, third floor, west side. He will give you a search warrant.
Return to Ali Tist, and ask to see his stock. He will finally give in. He will tell you that someone gave him a scroll, at which the end he found a cave full of boxes, and with a big locked door at the end.
He will give you a clue scroll. Report to Sir Tiffy again. They will give you a spare commorb to keep on contact.
The first clue leads to west of Falador. Dig to the east of the hallow tree to find another clue.
For the second clue, head south past the makeover mage. Pick an onion from the field south-east of the Crafting Guild, then head north. You will see a man wandering around. Use the onion on him, and choose wave. He will give you another clue scroll.
Head to the farm South of Falador. Search the lighter colored crate opposite the fireplace at the farm to find another clue.
Go to the monastery east of Ice Mountain. North of the north-eastern fountain on a red flower that has 3 blue flowers nearby.
The coordinates lead to a large hatchway north of the Black Knights' Fortress, north of Ice Mountain.
Jessika and Kurasi will teleport to you and help you open the hatch.
Kurasi will take care of the nearby guard. Talk to Kurasi again. She will try to talk to the Black Knight Doorkeeper. Talk to Kurasi again. Jessika will have a plan to summon a void drone to listen to the password.
She will summon it and give it to you. Look for some low boxes just west of the door, and use the void drone on it. Get it back after the cut-scene, and talk to Jessika again. Jessika will now get the password from the drone and try to get in.
You will need some identification from a worker that is leaving. Pickpocket a worker that is carrying boxes back. Try entering the door again. He will let you in, and Kurasi will overwhelm him. Have her tie him up and gag him.
Enter the last room, and search the north-west desk to get a tool. Use the tool on the south-west workbench to get a Metal strip. Search the north-west workbench again to get another tool, then use it on the north-east workbench to get another metal strip. Get yet another tool, and use it on the south-west bench. Use the three pieces together to get a Gaff.
Use the Gaff on the shef the key is laying on next to the north-west workbench to obtain the key.
It is largely suggested to use Magic, and bring a lot of food. It is LARGELY suggested to drain your own prayer to 0 before going in to fight them, as if you have any prayer points, the knight will drain it and heal.
Open the door when ready and attack the knight. When it's dead, talk to the pest cage. Talk to the Pest. After talking to it, make a decision with what to do with the pest. Go with Kurasi to the Void Knights' Outpost and report to Tyr. You will report in to Savant the situation.