National Geographic described him as "one of the boldest and best climbers in the world", and he won the 2019 Piolet d'Or for this free solo ascent of the Lupghar Sar West.

[4] He is perhaps best known for his 2007 free solo climb of the Via Attraverso il Pesce, commonly known as Fish Route, also on Marmolada's south face.

[1][4][5][6] The 37-pitch (850 metres, 2,800 feet) route, named for a fish-shaped niche in the 20th pitch, is highly committing, and is graded 5.12c (7b+).

[4] He subsequently focused on mountains of over 7,000 metres (23,000 feet) in the Himalaya and the Karakoram ranges, and was known for making several first ascents.

[7] Auer died on the descent after reaching the summit of Howse Peak in Banff National Park of the Canadian Rockies on 16 April 2019, with fellow Austrian David Lama and American Jess Roskelley.

[12][13] Photographic and GPS evidence recovered from the accident site and from Jess Roskelley's iPhone show they left their camp at the base of the east face at approximately 05:30 AM, climbed the first difficult ice pitch on M-16 by 07:19 AM, and then traversed left on new terrain into a left-leaning ramp.

After a pitch and a half up the ramp, they traversed left again and climbed an exceptionally difficult unclimbed waterfall, which brought them to a long, steep snow gully.