Oasis (quest)

Oasis is a Fallout 3 quest. It is also an Xbox 360 and PC achievement.

Objectives
Harold, a special FEV mutant from Fallout 1 and Fallout 2 (one of the only characters to appear in all three Fallouts along with Dogmeat) with a tree on his head which he called Bob, eventually found himself overwhelmed by it and became rooted to the ground during his travels in the Capital Wasteland region. Here he was discovered by several people who began to worship him as a god, and a small and exclusive cult known as the Treeminders began to form in secrecy. Bob began to blossom and many plants grew in this area, which became green with life, a stark contrast to the outer wasteland.

Harold reveals his true identity, and begs for mercy; after being stuck in the same position for decades he is eager for death. The other dwellers of "Oasis" have ignored Harold's wishes so far, and ask you to instead either suppress or expand Harold/Bob's fertility.

Birch gives you some sap that will cease Harold's growth, and Laurel gives you her liniment that will increase Harold's growth. Entry to the cave system is gained from the main Oasis hub area, not the doorway within the same area as Harold.

Instead of this you can just burn down Harold with any flame weapon. You will lose some Karma and there will be no Experience gain. The treeminders will become hostile as a result.

If you decide to go into the caves make sure to speak to Sapling Yew. If you succeed in the little speech challenge within the dialogue with her, this will unlock a reward after you return from the caves. An alternative is if you have The Child At Heart perk you will automatically succeed and will receive the award upon completion of the quest. This reward is given on either option for this quest, unless you fail in the speech challenge of course!

note actually there's a mistake, Harold is not a special FEV mutant from Fallout 1 and 2, he's a ghoul. The player finds him first with no tree on his head in Fallout 1 in the town of Necropolis if not mistaken. Then again in Fallout 2 in the town of Gecko, this time with the tree called Bob already growing on his head! So basically, yeah, Harold is a ghoul and not a mutant ;)

change by LBatalha

Walkthrough

 * After drinking the sap and awakening in the "Grove" look for Harold (The God Tree). Harold is in the middle facing away from the door to oasis (which is locked until you talk to him).
 * After talking to Harold exit to oasis and take your first left and keep walking until you come across a conversation between two Tree-minders.
 * Once you have acquired the Sap and the liniment, move to the fence door of the cave.
 * The cave has a lock that requires a lockpick skill of 100 to pick. Alternatively, you can ask for the key from the guard next to the entrance.
 * Once you enter the cave you have to navigate through. In the first section with the path alongside the shallow water there is one Mirelurk.
 * Once you get to the room with the large irradiated pool of water, you will encounter 1 Mirelurks, and 2 Mirelurk Kings. You will have to swim underwater to find the passage to move onward, from the path entering this room just straight ahead.
 * If you have an NPC companion with you, they will likely not be able to follow you as you swim underwater to reach the next space. However, once you go through the door mentioned below, they will be there with you on the other side.
 * Once you emerge from the water there will be a Radroach, then a Mirelurk. Continue on to a door further down the cave.
 * After you go through the door, there is a Mirelurk Hunter. A pathway off to the left (just after the door and before the Mirelurk Hunter) has a small alcove where someone used to live.  The skeleton is still there, surrounded by loot - including a Stealth Boy, Pre-War Book, D.C. Journal of Internal Medicine, a couple of Cherry Bombs, and Silenced 10mm Pistol.
 * Further along the path you'll pass another pool on your left side containing a Mirelurk. Diving in the pool reveals a couple of dead bodies with minor loot and a Mini Nuke.
 * Continuing on the path you'll see another skeleton with a Chinese Assault Rifle, a stealth boy, and 2 Ammo Crates. Just behind a stone divide is another Mirelurk Hunter.  Nearby is another skeleton with a Missile and some medical supplies.
 * Heading south, you'll hear a thumping sound. The thumping sound is Harold's heart. Walk up to it and you will be able to activate the heart, which gives you the 3 possibilities to proceed:
 * Destroy the heart.
 * Apply Birch's Sap (stop the growth).
 * Apply Laurel's Liniment (increase the growth).

After you made/applied your choice, there are 2 ways out; you can back track the way you came or proceed through the door to the Damp Cave. Choosing the way through the door can be a good choice since it is shorter and there are many valuable items along the way. When you go through the door and down the path, you will come to a ledge overlooking a large irridiated pool of water with some land you can jump straight down unto. They will be 2 more Mirelurk Kings and a Mirelurk swimming in or loitering near the pool. It's easiest to take them out one at a time (hopefully) from on the ledge. But be careful, as the Mirelurks will mysteriously teleport up to your location if you take too long to kill them from up there. Note the Missile and some minor items to the right on the ledge. After disposing of the Mirelurks, jump straight down to land. Then go right along the cave edge to find a skeleton with Sniper Rifle, Stimpak, Combat Knife, other loot and 1 ammo box. Keep going around right side of cave (brings you to north east corner) to find another skeleton with bottle of Nuka-Cola Quantum, two Nuka-Cola, a 10mm Pistol and other loot.

To get out of the cave, you're going to have to dive under the water (follow the quest arrow) and go through a door. This brings you back to The Grove with Harold in it. Depending on your choice, there will be Birch or Laurel waiting next to Harold, thanking you for your help on either option you chose.

Rewards
For destroying the heart


 * As a reward for this option you receive (immediately after destroying the heart) the Barkskin perk which gives you 5% additional damage resistance.
 * Sapling Yew will still offer you Yew's Bear Charm (so long as you passed the speech challenge). Find her on a bench near the Ceremonial Pit during the day.

For helping Harold grow


 * Bloomseer Poplar offers you the Poplar's Hood, which offers +10 Sneak and +1 Agility.
 * Branchtender Linden offers you Linden's Outcast Power Armor, which offers +5 to Big Guns.
 * Sapling Yew offers you Yew's Bear Charm (if you passed the speech check), which add 10 to your speech ability.

For stopping Harold's growth


 * Branchtender Cypress offers you a Missile Launcher + 1 or 2 Missiles
 * Branchtender Maple offers you the Maple's Garb, which offers +1 to Perception and +1 to Agility.

For setting Harold on fire


 * Negative Karma

Harold also has some more dialogue about your choice, if you chose not to kill him.

Assuming you didn't set Harold on fire and that you passed the speech challenge of Sapling Yew earlier you will receive Yew's Bear Charm from her upon completion of the quest (no matter what you did to the heart).

After destroying Harold's heart, talking to Father Birch and venturing back into Oasis a chat with Sapling Yew revealed a dialogue option along the lines of "I hear you may have something for me?", on activating the option you will receive Yew's Bear Charm (no Speech or SPECIAL check was shown - XBox 360). The availability of this dialogue option is not affected by the Lady Killer perk.

Bugs

 * Telling Fawkes to wait in the cave while the PC completes the quest may cause the game to crash or freeze when the player attempts to reenter the cave.
 * Sometimes Sapling Yew will not offer you the charm. This may be due to a glitch or simply not performing or successfully using the Speech challenge or Child at Heart dialogue.
 * Some dialogue appears to be missing in the PS3 version.
 * You will not be offered Poplars Hood after helping harold grow.
 * You will not be offered Sapling Yew's Charms after helping harold grow, there will be no speech options other than "What are you going to do now?" and "I have to go". (I've encountered this bug in the 360 version.)
 * In the Xbox 360 version, sometimes Poplar will not offer her hood after adding Laurel's Linament to Harold's Heart. (this could be a result of waking her up in order to ask for the hood, wait until she is awake)
 * Burnmaster is not considered a fire weapon by the game and will not burn Harold.
 * In the Xbox 360 version, sometimes you will recieve the barkskin perk after you apply Birch's Sap or Laurel's Liniment.
 * The initial ritual you must undergo to meet Harold will frequently not complete correctly. One or more of the NPCs will simply not speak, leaving you stuck without any discernible recourse. Loading from a previous save is the only way to continue.
 * If you anger Father Birch and/or Laurel (by making fun of their god) right before entering the cave to do something with Harold's heart, you won't be able to finish the quest, since you'll eventually have to speak to Father Birch at the end of the mission and he'll tell you to leave immediately. You won't have any dialogue options at all. If you did this and saved afterwards, the only way you can finish this quest is by setting Harold on fire.