Blood, Sweat, and Wild Steeds: Inside the Longest, Toughest Horse Race on Earth

Oct. 3, 2013— -- Think you have what it takes to finish the longest, toughest, most outrageous horse race on earth? The Mongol Derby is a bone-crushing sprint through more than 600 miles of rugged Mongolian Steppe. Thirty competitors from all around the world raced through hailstorms, downpours and oppressive heat in August all on the backs of 800 wild Mongol horses. Only 18 made it to the finish line.

This year was the race's fifth installment and for the first time, two young women were locked in battle for first place -- an unlikely rivalry that ended with a shocking twist.

"Nightline" traveled to the derby's starting line in Mongolia's vast wilderness, where it is believed man rode a horse for the first time 4,000 years ago, and followed this group of extreme adventurers, who paid up to $10,000 for the privilege to push their physical and mental limits.

Among this year's competitors were three Americans: Devan Horn, a 20-year-old hotshot from Houston, Lynne Gilbert, a lifelong equestrian -- and at 55, one of the oldest participants -- and Tom Burk, a 23-year-old Texan college grad, who somewhat ironically recently entered landed a job as a risk management analyst.

"I think if there's one thing I've learned about working in risk… it's that you got to take it when you can," Burk said.

The night before the race, derby organizer Katy Willings raised a glass of the Mongolian national cocktail airag, fermented mare's milk, for a toast. After the toast, Burk accepted a challenge from a native Mongolian -- a wrestling match. Unfortunately, Burk injured his shoulder and had to see the medic.

Day One started at 6 a.m. as riders made their final preparations. They are allowed just 11 pounds of gear, so luxuries like extra toilet paper are left behind.

At the starting line, Horn was raring to go. Gilbert came with a plan. She and her new friend from France, Sandra Fretelliere, formed an alliance to finish as a team. Meanwhile, Burk, with his arm wrapped up, was still dealing with the aftermath of the previous night's antics.

"Torn ACM or something, a bunch of ligaments, looks like I have a bone spur sticking out of my shoulder," he said, before saddling up.

With a final blessing from a Buddhist monk, the competitors were off on one of the wild Mongol horses, legendary beasts revered for centuries for their power and endurance, but feared for their unpredictable nature.

Horn was the first to reach the first horse station checkpoint and arrived alone. Being first meant she got first pick of a fresh horse.

"He's skinny, he's short, he's got nice legs and his feet are worn down so that means he rides a lot, so he's probably not crazy," she said, looking over one of the steeds before choosing one.

She checked the coordinates for the next station and was off.

Eventually, the rest of the pack started to arrive at the first station too, including Lara Prior-Palmer, who said she was turned off by Horn's Texas bravado.

"Some really competitive Texans and 'I'm here to win and if I don't finish in seven days, I'm not going home,'" she said.

Instead, the 19-year-old Brit had a different philosophy to surviving the race.

"You got to have sort of a 'anything goes attitude,' that you can deal with any situation because you have no idea what's going to happen next and I think that's what's so fun about it," Prior-Palmer said.