Cordyceps sinensis, commonly known as caterpillar fungus, is a unique parasitic fungus native to the high-altitude regions of the Tibetan Plateau and the Himalayas, thriving in cold, grassy alpine meadows above 3,500 meters. Traditionally, it has been used for treating fatigue, cough, hyposexuality, and renal dysfunction. The fungus contains several bioactive compounds, including nucleosides like cordycepin, polysaccharides, sterols, proteins, amino acids, and polypeptides, contributing to its pharmacological actions such as anti-inflammatory, antioxidant, antitumor, & immunomodulatory PMID: 25960753 
Its lifecycle is bizarre - Cordyceps sinensis parasitizes the larvae of the ghost moth, eventually killing and mummifying them before sprouting a fruiting body from the caterpillar's head. A 2014 systematic review PMID: 25519252 found that Cordyceps preparations, when used as an adjuvant therapy to conventional medicine, have shown potential decreasing serum creatinine levels, increasing creatinine clearance, reducing proteinuria, and alleviating some chronic kidney disease-associated complications such as increased hemoglobin & increased serum albumin.