Required quests/skills: Lost City, Nature Spirit. High farming is good.
Needed items: pair of secaturs, bucket of super compost, uncut diamond, and volencia moss (found on Karamja), some good food, and a bunch of transport runes.
Start: talk to Martin the Master Gardner in Draynor village. He wants you to talk to other members of GAG to find out what's wrong. Talk to 5 other gardeners. Most gardners will work for this, use the first option "Are you a member of GAG?"
The 5th gardener will tell you that Fairies are causing the problems. Go back and talk to Martin again. He'll want you to check it out, so go to Zanaris.
Go to where the throne is located. The queen's not there, so talk to the Fairy Godfather. He'll tell you that the Queen is sick, and go talk to Fairy Nuff.
Fairy Nuff is located back by the bank, just to the north. She'll give you a list of the Queen's symptoms and tell you to go see the head of the dark wizards, in the tower to the West of Falador. He'll help you, and want you to go talk to Morgas, who is the bumbling wizard along the highway south of Falador that keeps turning things in fungi. He'll help you with your quest by telling you how to kill the Tanglefoot. You need to take secaturs, super compost, volencia moss, and an uncut diamond to the Nature Spirit (in Morytania - from the Nature Spirit quest). Don't forget your amulet of ghostspeak!!
Once you get there, the Nature Spirit will enchant your secaturs. Simply make your way back to Zanaris. Head towards the Cosmic Temple Ruins, and there will be a crack in the wall you can squeeze through. Follow the path around until you get to the end. Attack the Tanglefoot (level 111) while wielding the secaturs. Once you kill him, he'll drop the Queen's secaturs. Take those back to the Fairy Godfather to complete the quest.
Reward: farming xp, magic xp, and 2 quest points