Mushroom of Immortality

Mushroom of Immortality is not really an artefact, but a naturally grown mushroom found in a specific place.

History
Mushroom of Immortality is found in a cave in China, somewhere in Yunnan province. They seem to have healing properties, but only during certain seasons. Picked at the wrong time the mushroom is lethal.

In 1996, Robert Demur accidentally found the mushroom with another student while on his graduate fieldwork expedition, but the sample disintegrated before they could study it. Robert Demur continued to study references to the mushroom back home.

In 2016 Robert Demur returned to the cave with Lara Croft and Knighthood of the Dark Spore. Lara found the source of the mushrooms, it being a dead body deep in the cave system. Lara marked the location with a GPS signal.