They called it saola, a local name, and also the Vu Quang ox. Formally described in the journal Nature in 1993, it became Pseudoryx nghetinhensis — the species name built from Nghệ An and Hà Tĩnh, the two provinces whose forests it haunts. It stands about 84 centimetres at the shoulder and 150 centimetres nose to tail, weighs 80 to 100 kilograms, and wears a chocolate-brown coat marked with white on the face and a dark stripe down the spine. The horns run 35 to 50 centimetres. Journalists reached for "Asian unicorn," partly for the rarity and partly for the reported gentleness of the few animals ever held in captivity, none of which survived more than a matter of weeks or months. No trained scientist has ever seen a saola alive in the wild. Every photograph in existence was taken by a camera the animal tripped itself.

The saola was not a one-off. In 1994, working the same forests of Vũ Quang and central Laos, researchers described the giant muntjac, Muntiacus vuquangensis, the largest of all the barking deer at 30 to 50 kilograms and, like the saola, now listed as critically endangered. Five fish species new to science came out of the same catchments, among them Parazacco vuquangensis and Oreoglanis libertus. A new oak, Lithocarpus vuquangensis, was described from the park as recently as 2018. There were also loose threads that never quite resolved: a skull and some meat handed to the zoologist George Schaller in 1994 belonged to Heude's pig, Sus bucculentus, a species named in 1892 and then effectively lost, with no physical evidence secured for a century. For a few years in the 1990s, this stretch of the Annamites was the most surprising forest on Earth.

Long before biologists came here, Mount Vũ Quang was a headquarters. When the Cần Vương movement rose against French rule on 5 July 1885, the scholar-official Phan Đình Phùng — born in Hà Tĩnh, a first-place graduate of the imperial examinations, and a censor who had made enemies by refusing to overlook corruption — established his base on this mountain, within sight of the coastal plain where the French held Hà Tĩnh. He split his territory into twelve districts and built a network of camps, food caches and village contacts across four provinces. His commander Cao Thắng reverse-engineered captured French rifles and turned out roughly 300 copies, the springs improvised from umbrella spokes. Cao Thắng was killed leading a frontal assault in September 1893. The French arrested Phan's family, dug up his ancestors and displayed the remains publicly to force his surrender; he did not surrender. Sick with dysentery and carried on a stretcher through the last months, he died on 21 January 1896, and the men taken with him were executed.

The area was declared a forest reserve in 1986 and elevated to a national park in 2002, covering 550 square kilometres of Vũ Quang District in Hà Tĩnh Province, managed by the provincial People's Committee. It is high, wet, close to the Lao border, and thinly walked. Conservation work here has shifted from discovery to holding on: community-based projects protect the critically endangered northern white-cheeked gibbon, and rangers spend much of their time pulling wire snares out of the undergrowth, since it is snaring rather than logging that empties Annamite forests of their largest animals. Whether the saola still exists is an open question — the last confirmed record anywhere was a camera-trap photograph from central Vietnam in 2013, and a 2025 genomic study placed the northern population squarely in Vũ Quang, Pù Mát and the Lao forests over the ridge. The mountain has hidden things successfully before. It would be entirely in character for it to be hiding one more.