Oasis - Fallout 3 Wiki Guide - IGN (2023)


  1. Undertake the Treeminder's Ceremony.
  2. Enter the caves below and destroy Harold's Heart.
  3. (Optional) Kill Harold by burning him.
  4. Speak with Tree Father Birch.



  • Lawn Mower Blade
  • Tin Can (M)
  • Empty Soda Bottle (M)
  • Grimy Pre-War Businesswear
  • Darts (M)
  • Pre-War Book
  • Bottle Caps (M)
  • Nuka-Cola
  • 10mm Rounds (M)
  • Silenced 10mm Pistol
  • Abraxo Cleaner
  • Flamer Fuel (M)
  • Missile (x2)
  • Mini Nuke.

Part 1

In the far, far northern end of the Capital Wasteland, almost directly in the middle of the map (and due far, far north of Megaton) is an isolated and hard-to-locate settlement called Oasis. Finding Oasis simply isn't easy, because there's only one way in and one way out, and the pathway to the settlement is obscured and difficult to find. Here's the best way to try to locate it. Up in the center-northern segment of the map, you'll find something called the Clifftop Shacks. When you first arrive there, you'll find Super Mutants and a human prisoner and little else, but this is a fairly easy location to find atop a precipice looking southward over the expansive Wasteland. From there, travel northwest until you reach a chasm, and begin working your way around that chasm (which will actually bring you in a northeasterly direction for a while -- seemingly antithetical to your approach). If you swing around this chasm and keep a keen eye, you'll eventually see a path leading back into the mountainous area you were previously avoiding. This is the pathway to Oasis.

Head down the linear path as it thins and rises slightly in elevation. When you've traveled far enough, you'll find the wooden gate to Oasis guarded by two of the settlement's residence. Immediately, you'll notice something suspicious about this place (though not necessarily in a bad way). Trees are growing normally and are in full bloom; perhaps the only outdoor place in the Wasteland where this is happening. And the two guards at the door, while normal looking people, seem well-clothed and well-armed. Was this place somehow isolated from the atomic blasts? Or did they somehow grow anew these plants and create a more habitable place for themselves? Regardless of what's going on, speak to one of the guards, Tree Father Birch, and follow him inside the settlement when he invited you to join him.

Tree Father Birch will head on inside, leaving his associate at the front gate. Follow him inside. He'll walk towards something identified as The Pavilion -- follow him to where he sits on what appears to be some sort of throne, and then speak with him again. When you do, you'll be able to converse with him about Oasis, its history, and about the people that live there. It appears Oasis was stumbled upon by some people (presumably out friend Father Tree Birch was among them) about two decades ago. Since finding this pristine place, the residents of Oasis have taken care of and defended Oasis from a harsh outside world. They owe it all to Him, an oft-spoken about character who you'll eventually realize is most likely their unknown deity.

When your conversation with Father Tree Birch winds down (be nice to him, or you risk hostilities, which will cut you off from getting anywhere on this quest, good or bad!), he'll invite you to take part in a sacred ritual which all of the people of Oasis partake in. It has to do with the sap bucket in the middle of The Pavilion, but before you drink from it, you'll have to wait for the half-dozen or so residents of Oasis to join you around The Pavilion. Then, you can drink from the sap, which will make your character hallucinate. After listening to the prayers spoken by the people of Oasis, it appears your character faints, only to be transported to another part of the settlement.

This beautiful, serene place you wake up in after fainting is perhaps more untouched than the previous area you explored before the ceremony. You won't be able to backtrack (the door leading backwards is locked and can't be picked), so explore the environs surrounding you. The point of interest here should be incredibly obvious -- there's a tree with a face that you can talk to. The Talking Tree goes by a couple of names and speaks in convoluted and seemingly-nonsensical ways. It's unclear exactly what he is (though it appears he and a friend are both human... or were, at one time). You will find out that the two men were exploring a military base called Mariposa, however, something familiar enough to Fallout veterans.

The Talking Tree's request is easy enough. He wants to die, and he wants to die badly. He's not human anymore, but a sedimentary tree, unable to move, eat, read, or do anything else that would otherwise invigorate the human soul. But as you continue to talk to him, you'll realize that you can't just shoot him or burn him down or anything. Instead, you have to travel to an underground cavern where the tree's internal organs are located -- his heart included. Eliminate his heart, and the Talking Tree will die as requested. To find the entrance to the underwater cavern, head to the top of the area, where you'll find a pool of irradiated water. Swim into and under the water and you'll find a door to pick open. You just want to pick the lock right now; once it's picked open, backtrack to dry land and approach the door that was previously locked. You can now go talk to the villagers before proceeding.

You won't be able to just destroy the tree's heart. You'll have to actually apply a substance to it, which is where the villagers come in. The villagers deviate from one another on how to actually handle the situation, and while some of the villagers will concur that if the tree wants to die it should, others aren't so sure that the insane growing power of the tree shouldn't be harnessed for a greater purpose (of course, if you're downright evil, you can just cut to the chase and burn the tree down with your Flamer posthaste, though you won't exactly be able to conclude the quest as intended). The primary deviation comes from Tree Father Birch and his wife, Leaf Mother Laurel. Birch wants to stymie the growth of the tree's heart to contain Oasis and therefore not give away their natural habitat to possibly-hostile outsiders. Laurel wants you to exacerbate the situation by making the tree's heart more robust, thus making growth increase rapidly outside of Oasis. Both will give you items so you can make the right decision when the time comes (though there technically is no right decision -- you can do what you want).


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Part 2

With this newfound information, you can now head back towards the talking tree and then back into the water and through the door you previously unlocked. Now, this upcoming area can be difficult for gamers who aren't too far in the game, simply because the water is irradiated and you're going to be in or around it for the duration of our journey through this aqueous cavern. What's more is that this is an aside to the quest at hand, but should still be done, regardless of the radiation. Combating it is easy if you have a lot of items -- RadAway will get rid of your radiation, while Rad-X will boost your radiation resistance. Both are great items to spam here, but go easy on your supply! You need those items elsewhere, you know!

As soon as you enter the cave, continue to swim forward, coming up for air before submerging yourself once more to continue along the linear path (there's no overland route). When you enter the cavern ahead, you're likely to be attacked by a trio of Mirelurks. The scaling nature of Fallout 3 will differ slightly the variety of Mirelurk you meet, but if you're even remotely through the game's main quest, chances are you'll encounter at least one powerful Mirelurk King here -- perhaps two. Either way, fell the initial wave of enemies and then backtrack out of the cave, and back to dry land. That's right, we're done here for now. But you'll thank us later when those enemies are dead!

To get to the actual part of the cave we need to traverse, we have to head back to The Pavilion, and then go rightward, taking the topmost of the two branches. Here, you should find a man named Branchtender Cypress walking around. Speak with him briefly and ask him for the key to the caves, and he'll hand it over as if it wasn't even a big deal. Conveniently, the key he gives you opens the oddly-new looking chain link fence behind him at the end of the path you found him on. Open it up and head into the cave.

The cave is fairly linear in the early-going, so you shouldn't have any trouble navigating the cave from the outset. And although there's watery noises all over the place (especially apparent with headphones or surround sound), you can actually dodge the highly-irradiated water for the most part while navigating this cave. Head forward from the entrance, and keep going forward until a Mirelurk is seen ahead. Down the Mirelurk and proceed down the pathway, swinging left at your first opportunity (heading forward will shortly thereafter bring you to a dead end). Traversing this new branch of the path will run you into another Mirelurk enemy, but it's the wide open cavern that foes was guarding that's of true interest.

This cavern will undoubtedly be full of Mirelurks, so be ready for a firefight. When you've downed all of those enemies, there's little reason to stay in this cavern, so jump into the irradiated water (again keeping in mind that weaker players will want to rely on Rad-X and RadAway to survive possible radiation poisoning here), seeking out the only open area underwater that leads to an adjacent corridor (there's really no way of getting lost here -- just keep that Pip-Boy light on!) Traverse the completely linear corridor on the other side of the water, fighting more Mirelurks as you go. There's simply no getting lost here -- just walk, walk, walk and fight, fight, fight until you reach a wooden door that leads to the Sunken Chamber.

We're getting close to our objective point now. Head forward down the quiet, linear path. When you find a path branching off to your left, be sure to take it, as this alcove holds some of the only items of any use you'll find in the environs in or surrounding Oasis. The lawnmower near the split in the path contains a Lawn Mower Blade if you want it. Then, down into the dead end alcove itself, you should find plenty of items, including a pair of Crutches, a Pre-War Book, some Bottle Caps, a Nuka-Cola, Abraxo Cleaner, and perhaps most valuable of all, a Silence 10mm Pistol and a plethora of 10mm Rounds. Nice!

Rejoin the original path and continue your linear trek. You'll be able to proceed through an innocuous area for a brief time before being accosted by more Mirelurk minions. Around the time when this happens, you'll see a deep pool of water to your left. Now, there's no reason to jump in here to proceed, but if you want an extremely valuable Mini Nuke to add to your inventory, than you should jump in, submerge yourself for a brief time, and grab it. Then, rejoin the path and continue along it, keeping an eye out for more enemies. Other than some ammo lying on the left side of the path (in the form of Flamer Fuel and a couple of Missiles), there shouldn't be any other items to grab here.


But... what's that noise? That distinct pitter-patter. Of course! It's the tree's heart! You'll know you're getting close to its location when you begin to hear the heart's beating in the background. The closer you get, the louder it will be, so it makes for a great way to find your way (though the pathway isn't exactly hard to traverse without this hint). When you find the heart, walk around the myriad roots that are protecting it. You should be able to examine it, and you'll be given an option of what to do. Will you bleed the heart outright, killing the tree as it requested? Will you apply a substance that will force the tree's heart to stop growing? Or will you puncture the heart with an ointment that will force it to grow even quicker, spreading its green growth all over the Wasteland? What you do (and what you earn as a result) is up to you, but remember! -- there's no negative karma to be gained here unless you outright burn the tree with your Flamer aboveground. When you're done here, you'll also be happy to know that adjacent to your position is a door leading into an adjoining cave. No annoying backtracking necessary!

This adjoining cave, as you may have guessed, was the cave we briefly visited earlier in order to clear it of Mirelurks. The reason we did that is simple. It figures that after some battling with Mirelurks in the actual caves, you'll want a brief, clean getaway. And as long as you followed our instructions, not only will you be able to blaze through this alternate cave extremely quickly, but you won't have to deal with any enemies either! And since you need to talk to Tree Father Birch to conclude the mission, you'll come out near the tree you just destroyed, which is coincidentally where Birch is waiting. Speak with him (regardless of which path you chose) and conclude this side quest for good.

Up Next: Post-Apocalyptic Plumbing

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Top Guide Sections

  • Basics
  • Main Quest
  • Side Quests
  • Appendices
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