Oasis is a location in northern wasteland... with green trees. It is in an isolated area within the mountains, with a pathway allowing entrance from the west.
After entering the oasis, you are informed of a special request and that you are to be welcomed into Oasis to speak with Him. After a short ceremony, you get to speak with Him.
He originally was exploring a military base called Mariposa, and was attacked when leaving an area filled with green goo.
Harold's request is for you to kill him. He was stuck in a location for two decades, with a tree called Bob growing out of him. The tree has completely enclosed him, leaving him to remain in a single are with only the Treeminders as friends.
When you return outside and approach the caves, you see the two leaders arguing with each other about what to do with Harold. They both give you items which can either stop or accelerate the growth of the heart.
While you can burn him directly, that's causes negative karma.
The caves under oasis lead to Harold's heart. You will have to swim through a few areas with Mirelurks.
When you come into the sunken cavern, take a left turn, and examine the pile of objects. Among them is a Pre-war book, DC Journal of Internal Medicine, and a silenced 10mm pistol.
The three options
- Destroying the bark gives you the Barkskin perk, with gives +5% damage resistance. It upsets the Treeminders when they see they realize that they mistook his words for a mystical sign.
- Linden gives unique power armor will give you power armor if you accelerate the growth and Laurel will give you headwear that improves Agility and Sneak.
- Cypruss will give you two missiles if you stop the growth, and Maple will give clothing that improves Agility and perception.