Black Knights' Fortress

He tells you that the Black Knights have started demanding a lot of money from Falador, and threaten to invade the city if it's not complied. Although he doesn't take the threat seriously, he feels uneasy at the black knights' mention of a powerful, secret weapon and will ask you to check on them. He hands you a dossier for more information.

The fortress is located north of Ice Mountain, just south of the Wilderness wall. The fortress is not very far from Edgeville, so players may simply home teleport to Edgeville and run south-west to reach it. To gain access to the fortress, you will need a bronze helm and an iron chainbody. Additionally, it can be time-saving if you obtain a cabbage from anywhere, except Draynor Manor. A cabbage can be picked from the Edgeville Monastery on the way to the fortress.

Before entering the fortress, equip the helm and the chainbody. Enter the sturdy door on the south side of the fortress. As you are disguised amongst all the guards, you will be permitted to enter into the fortress, hassle-free.

Since it is not necessary to keep the guard disguise once in the fortress, better armour may be used for greater protection.

After entering the fortress, go through the fake wall directly in front of you.

Climb up the ladder twice, and you will be on the roof.

Go south and climb the ladder down one floor.

You will see a door to your east; go through it and take the ladder up.

Head down the ladder immediately next to you, and you will find yourself in a room with an altar.

Exit the room and climb down the ladder south-west of the room. Go down the pathway, and you will find a ventilation grill at the end.

Listen-at the grill, and you will eavesdrop in on a conversation below you. Apparently, the Black Knights have commissioned a witch to brew them an invincibility potion to fight against the White Knights. Part-way through the conversation, the witch orders her goblin servant, Greldo, to bring a cabbage growing in Draynor Manor, and that any other cabbage would only wreck the potion.

Make sure you have a cabbage with you, and return to the entrance of the castle. Once you're there, go into the banquet hall to the east, filled with all the knights. When you try to enter the room, you will be notified that the knights are in an important meeting and that anyone who tries to enter the room will be killed. Enter the room anyway.

In the hall, climb up the ladder in the north-west corner of the room. Walk south-east, through the hallway, to reach a wall. Push it open and you will see a hole in the floor, which is coincidentally, placed just above the witch's cauldron.

Right-click on your cabbage and use it on the hole. A cutscene shows the witch waiting for Greldo to return while your cabbage drops down into the cauldron, ruining the potion and the Black Knights' plans.

Now that you have successfully foiled the Black Knight's plans, return to Sir Amik Varze and inform him of the good news. He will be pleased and reward you.