Oasis (quest)

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

Objectives and Walkthrough
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.

The Ritual
When the player approaches Oasis, Tree Father Birch will ask that the player follow him, saying that "He" has summoned him/her. If agreed to, Birch will unlock the gate to the village and lead the player to an outdoor hut. Birch explains that he is the leader of the Treeminders, and that "He" has summoned the player to the village. Although vague about who "He" is, wishing the player character to find out on their own, a Speech Check may be passed to discover what "He" is. The Treeminders ask that the player drink a sap in a ritual to purge the PC of all evil that might be inside him, so that "He" may go unharmed.

Afterward the ritual, the PC is placed in The Grove, where they meet Harold. 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.

To your left after leaving The Grove you will witness an argument revealing that Tree Father Birch wishes to stop Harold's growth with a sap in order to protect him, and Leaf Mother Laurel wishes to apply a liniment that will accelerate it, to spread his influence to the entire wasteland. They both speak with you in turn and ask you to ignore the other's wishes and side with them.

So you are left with three choices:
 * Side with Birch and apply Birch's Sap to Harold's heart to stop his growth.
 * Side with Laurel and apply Laurel's Liniment to Harold's heart to accelerate his growth.
 * Side with Harold and destroy his heart, killing him in the process.

Instead of these options, Harold may be burned down with a fire-based weapon. If this is done the player will receive negative Karma and all of Oasis will become hostile.

After the Argument
The rest of the Treeminders are converseable at this point, who will express their views on the situation. Your reward is based on what you decide to do to Harold's heart and who you speak with before entering the caves.

Regardless of what you choose to do to Harold's heart, speaking with Sapling Yew beforehand is recommended. If you ask her about her "god" a speech check will become available allowing you to discover Harold's fear. If you pass the speech check (discovering that Harold is afraid of fire) but choose not to burn him down to complete the quest, she will give Yew's Bear Charm after completion of the quest. The Child at Heart perk can be employed as an alternative to guarantee success.

If you plan to side with Birch.
 * Speak with Branchtender Maple before entering the caves and ask her about how she ended up in Oasis. She will tell you about how she felt that she was chosen to come here and fears that outsiders will eventually find and ruin the Oasis.  Pass a speech check to convince her that Oasis is off the beaten path far enough to stay hidden, and after applying Birch's Sap she will give you Maple's Garb as a token of her thanks.
 * Speak with Branchtender Cypress before entering the caves and ask him how he became a Treeminder. He will tell you about how Birch took him in and and told him how important it is to keep Oasis a secret from the outside.  Tell him "I think you are right" about keeping it a secret, and after applying Birch's Sap he will reward you with a Missile Launcher and some Missiles from his former life.

If you plan to side with Laurel.
 * Speak with Bloomseer Poplar before entering the caves and ask her about "her god." She will inform you that Harold is not only her god but everyone's god and should be shared with the entire wasteland.  Tell her that you agree completely that Harold is for all mankind, and after applying Laurel's Liniment she will give you Poplar's Hood in gratitude for helping Harold grow.
 * Speak with Branchtender Linden before entering the caves and ask him how he ended up in Oasis. Pass a speech check and he will tell you that he was once a Brotherhood Outcast and was found injured by the Treeminders and nursed back to health by Bloomseer Poplar herself.  After applying Laurel's Liniment (which of course pleases Bloomseer Poplar) he will give you his Linden's Outcast Power Armor as a gift.

If you plan to side with Harold.
 * There is no need to speak with anyone prior to entering the caves. After destroying the heart the player will be exposed to Harold's mutation and grant the player the Barkskin perk which grants 5% Damage Resistance.

In order receive the gifts at the conclusion of the quest, you must speak with the gift givers BEFORE you enter the caves and interact with Harold's heart. If you don't do this, they will NOT give you their gifts after the quest is over. (This is confirmed on the PS3 version)

NOTE: After completing this quest on the 360 version WITHOUT talking to any of the treeminders (except the 2 that give you the sap) and returning to the one you finished the quest for, he/she will tell you that 2 of there people have gifts for you. they will give you the exact same items that they would if you talked to them.

however, you must talk to yew for the bear charm.

Into the Caves
The main entryway to the cave system is in the main Oasis hub area. The player can either pick the lock (100 Lockpick required) or ask Branchtender Cypress for the key.

Resistance in the Oasis Caverns mostly consists of various Mirelurks, along with the odd Radroach. NPCs will have trouble following through the mess of underwater tunnels, so they should be left outside. Strangely, some dead wastelanders are in here. There's plenty of decent loot to be had in the tunnels, so search extensively. A D.C. Journal of Internal Medicine is just inside the sunken chambers. When you enter take the first left. It is inside of a crate with a baseball glove and baseball.

In order to advance, going underwater is necessary at times, so if it doesn't look like there's a way through, try checking underwater. Near the end of the Sunken Chambers, a thumping will be heard. This is the sound of Harold's heart. When reached and interacted with, the options mentioned before will present themselves to the player. Pick your action then continue.

A nearby door will lead into another subcavern, which will lead back to the Grove, where either Birch or Laurel will be waiting depending on your choice. If the heart was destroyed, Birch will be there, and express regret over not listening to Harold.

At this point you will be able to receive gifts from the Treeminders that you spoke with before entering the caves. The Treeminders may also be spoken to after this to get dialogue about your decision. Harold also has some more dialogue about your choice, if you chose not to kill him. If the player chose not to kill Harold, they may still burn him after getting the rewards and move on with Plan C for some negative karma.

Bugs

 * If Tree Father Birch is killed, all of Oasis will turn hostile against the player. However, this happens even the player wasn't the one to kill him (e.g. an enemy was lured over before starting the quest). Strangely, the same won't happen if Branchtender Maple is killed in this fashion.
 * If the player does not stand across from Tree Father Birch during the ritual, it may not complete correctly, effectively forcing the player to reset.
 * Occasionally, Oasis will be locked for no given reason. If this happens after starting the quest but before finishing it, it will be impossible to complete. This will also effectively cause Birch's Sap and Laurel's Liniment to permanently take up weight in the player's inventory. On very rare occasions, it is even possible for the door to lock while INSIDE Oasis, although in that instance, it is possible to escape if Tree Father Birch is killed and the Key to Oasis is retrieved from his body.
 * The Burnmaster is not considered a fire weapon by the game and will not burn Harold.
 * When approaching Birch and Laurel after seeing Harold, if the player gets close enough so they can hit them with a melee or unarmed weapon in V.A.T.S., but not close enough to trigger the conversation, and tries to attack either in such a fashion, the first two lines of their argument will take place in slow motion with a shaky camera.
 * When approaching Birch and Laurel after seeing Harold, it's possible to get close enough to speak with them, but not close enough to trigger their conversation. If this is done, they will immediately go into their dialogue about their tasks. The trigger point still exists, though, and stepping near where it was will trigger the conversation (even if they're walking as they do so).
 * In Laurel's case, the two will immediately walk off after her dialogue is over. Birch's dialogue will never happen, so the player cannot get out of the control loss that happens when the conversation starts, making it impossible to proceed. Speaking with both has a similar effect.
 * However, if Birch is spoken to, the entire conversation can be effectively skipped. If it is triggered after his dialogue is over, Laurel will start saying her lines, and after a few moments, approach the player to give her dialogue. Control will be regained afterward, with the conversation continuing as the two walk off. It should be noted that if Laurel speaks with the player in this fashion when he/she has not triggered the conversation, there will again be no way out of it.
 * 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.
 * The ledge in Damp Cave leading to Harold's heart can be reached from The Grove's side. Inside, there is a Mirelurk King and two Mirelurks waiting. Kill the Mirelurk King and one of the Mirelurks, and get the remaining Mirelurk's attention. Then, scale the cliff near the door to the next area, starting from the rocks on the right side (not the little shoreline just below it). Usually, the Mirelurk will mysteriously teleport on top. Get its attention again if it was lost (i.e. a Stealth Boy was in use), get as close as possible, then go into V.A.T.S. and try to hit it. The player character will teleport onto the cliff as well to attack the Mirelurk. However, the door will require a key to open (neither the Key to Oasis Caves or Key to Oasis will unlock it).
 * The Sap and Linimint may not weigh anything until either is applied.
 * Sometimes, Sapling Yew will not offer you her charm, even if the Speech Check/Perk Check is completed.
 * If the Treeminders are angered through dialogue, the cave may still be entered with 100 Lockpick. The heart can still be reached, and the Barkskin perk can still be obtained. Strangely, the Sap or Liniment can be applied despite not having either. Harold will react accordingly through dialogue to this. However, as the only way to complete the quest is to speak with Birch/Laurel, and they will only say to leave when spoken to, again, Harold must burn if the quest is to be completed. If the Barkskin perk is obtained, Harold will not be able to be burned, leaving the quest permanently incomplete.