(Capcom's primary storyline)
Stairway of the Sun, also called Sonnentreppe in German, is a species of flowering plant native to West Africa, and belonging to the family Asteraceae, which includes such flowers as the Chrysanthemum.
The name "Stairway of the Sun" along with its German name relates to the Sun Garden, an ancient stone garden constructed by the Ndipaya untold centuries ago. Within the garden there are steps leading up to a mound where the flowers grow naturally. The steps and flower are, therefore, synonymous. The Sun Garden is likewise known because of a hole in the cave's ceiling that allows sunlight to penetrate the underground.
Stairway of the Sun evolved within the Sun Garden before the Ndipaya inhabited the cave. Within the DNA of the flowers is a retrovirus known as Progenitor, which the flowers only actively produce under the unique conditions of the garden. Cultivated flowers outside the garden will not produce the virus unless they are exposed to identical conditions ranging from soil to sunlight.
Stairway of the Sun became central to Ndipaya tradition untold centuries ago, when the West African tribe began exploring caverns near their wetland territory. The flowers were toxic to most who consumed it, the result of disease caused by viral infection. Every so-often a man would eat from the garden and survive infection, gaining superhuman strength and intelligence. Over the centuries a highly sophisticated society of engineers developed around the plants, and formed a stone city in the caverns. The city itself was destroyed by mutant animals that also ate from the flowers, which ran amok and killed their King. Though the Ndipaya ultimately succeeded in defeating the monsters, numerous claimants to the Kingship perished from the disease, the last attempt being in the 1960s when Umbrella Pharmaceuticals sent mercenaries into the ruins to take the garden for themselves. In the decades following, the flowers were cultivated continuously by Umbrella and later Tricell, for virological research ranging from eugenics and creation of a new human race to improvement of mutant animals.