Tears of Guthix (quest)

Getting Started
To start, you need to find Juna deep inside the caves under the Lumbridge Swamp. You'll need a bullseye lantern to get deep enough without being attacked by the creatures that live in the darkness. You don't have to make it yourself, as a player with high enough Smithing and Crafting can put one together for you, but you must be able to light it yourself. To get to where Juna is, you will need a Spiny helmet or have started the Lost Tribe quest.

You can get a Spiny helmet from Slayer Masters. If you have one, you can enter the cave from the swamp, travelling south, then hugging the south wall all the way until there's a place where you can jump on a rock to cross a small, subterranean river. South of the frogs is a cave entrance. From there, head east, climb down the slope, and continue east until you see Juna sitting in front of the cave. Talk to her to begin the quest.

If you have at least started the Lost Tribe quest, you won't need the helmet. You can just go to the basement of Lumbridge Castle, climb through the hole in the wall, head south, then climb through the hole to get into the cave. From there, head straight south to the frogs.

Juna
When you talk to Juna, she will tell you some stories about the Tears and tell you of how very bored she has become. She's willing to let you into the cave for a little while to gather some of the miraculous Tears of Guthix, but first, she has a task for you. To collect the tears, you will need a stone bowl. Getting there will be a trick, though, since you can't quite climb up to where the rocks you need are.

The Light Creatures
In the big black place in the middle of the area are a group of floating orbs of light called light creatures. For this next part, you may want to work fast, since taking too long can mean taking some good damage. The creatures of the cave hit very fast.

Extinguish your lantern and use your cut sapphire on it. You'll switch out the normal lens for the sapphire, making a Sapphire lantern. Use your Tinderbox to light it again, then head to the entrance of the area, up the rocks that you climbed down. Use your sapphire lantern on one of the Light Creatures to lure it closer. At that point, it will pick you up and give you a ride to the other side where the rocks are.

The Bowl
Use your pickaxe to get a magic stone and then use your chisel to craft it into a bowl. One will be enough. Now head north to climb back down and head back to Juna. Give this bowl to her, and your quest is complete.

Rewards

 * 1 quest point
 * 1,000 Crafting experience
 * Ability to play the Tears of Guthix (minigame) once a week.