There was once a woman who loved a sad man with a hole in his heart. The harder she tried to fill it, the more drained she felt. When there was nothing left of her, she killed herself under an old tree and let its roots drink her blood. Soon after, the sad man disappeared from the settlement. The tree bore a tear-shaped fruit.
If you can see the Lonely Tree for what it really is, it's probably too late. This carnivorous organism hypnotizes anything that comes near, luring prey with hallucinations of their innermost desires. Once they draw near, the hallucinations turn to ceaseless dreams, while the roots consume the victim in their sleep.
With each meal, a grotesque bulge, appears on the Lonely Tree's branches which slowly swells and takes on certain qualities of the devoured as they are digested. This "fruit" of the Lonely Tree is its true prize, as eating these conglomerations of phytohormones and human gristle can have beneficial (albeit bizarre) side effects. However, make sure to handle them gently while they are close to the tree, as the chemical volatility of the unripened morsels doubles as the Lonely Tree's primary form of self-defense!
The Lonely Tree expansion adds the Object of Desire hunt event to the basic hunt event deck. Encountering this hunt event causes the Lonely Tree to appear during the next showdown, dropping "fruit" on the ground which both survivors and the monster can interact with. After resolving the Object of Desire hunt event, the card is archived, meaning that you will only experience the Lonely Tree once during a hunt.
The Lonely Tree can return as a Nemesis showdown if survivors choose to consume the Lonely Fruit strange resource card.