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 Fallout's as well as 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!

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 look around (without exiting to the wastes) 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 2 Mirelurks, and a Mirelurk King. 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; one through a door in the room, which leads to a room with 2 more Mirelurk Kings and a Mirelurk that are very close together as well as another irradiated pool of water you will have to swim into to escape, or you can back track the way you came. Choosing the way through the door can be a good choice since it is a shorter way, there are some items (including a 10mm and a Sniper Rifle near the corpse on the right after entering/jumping down) in the cave and some ammo lying around + 1 ammo box. Be sure to pick up the bottle of Nuka-Cola Quantum that is just North (among some other minor loot) of the previously mentioned corpse. It can/will happen that some of the Mirelurks will mysteriously teleport up to your location, if you choose to stay on the upper part of the cave and try to kill them from up there.

After the fight you just dive again, and will end up, after passing the last door, in the area 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.

For helping Harold grow


 * Bloomseer Poplar offers you the Poplar's Hood
 * Branchtender Linden offers you Linden's Outcast Power Armor

For stopping Harold's growth


 * Branchtender Cypress offers you a Missile Launcher + 1 or 2 Missiles
 * Branchtender Maple offers you the Maple's Garb

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).

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.
 * In the Xbox 360 version, sometimes Poplar will not offer her hood after adding Laurel's Linament to Harold's Heart.
 * Burnmaster is not considered a fire weapon by the game and will not burn Harold.