Black knights fortress
start; In the city of falador, go to the white knights castle and speak to sir amik.
Step1:Go to the Cabbage field at monastery and take 1 or more cabbages, then go to
Black Knights Fortress (located at the ice mountain, a bit west of Monastery)You'll notice the front door is locked, and the guards won't let you in the side door. Why? You don't look like them. To get in u need a Guards uniform, Medium Bronze Helmet and Iron Chainmail.
Step2:Go through the "odd looking wall" which is at the north Wall when u get in, go up the ladder.U see a "Grill" and u can choose listen by left clicking it, u will see the Black KnightGoblin, and the witch will start to speak to each other. It's an invincibility potion they're making, and it needs acabbage from Draynor Manor to be complete. Any other cabbage will destroy the potion.
Steap3:Go back down the ladder, you see a room next to you with 3 Black knights, go in there, the Guards says you shouldn't go in there, because the black knights are going attack you.When u get in there,1 Black Knight will attack you,but just run from the fight or kill the Black Knight if u can.If u press the other door in the room, a Black Knight will attack u, so make sure all Black Knight are busy if u want to go through the door, (good to get friends with u attacking the Black Knight's).
Step4:Go upstairs, climb the ladder, at the north wall is a "odd looking wall". go through it and "use cabbage with hole"If you made it correct u will say "that must have ruined the secret weapon" or something like that
reward: 2500gp and 3 quest points.