Even when Sister Shred isn’t donning a nun Halloween costume, she doesn’t fit the typical mold of a daredevil dropping off boulders on a mountain bike or carving steep slopes and deep powder on a ski bike.

But any chance she gets, Kris Nordberg, 65, also known as Sister Shred, will do exactly that, in spite of a rare vascular condition that has rendered her legally blind.

By riding with her head turned to the side, she can use her peripheral vision to make out people ahead of her on the trail and shapes and colors. And, for the most part, that’s enough to keep her seeking adrenaline-fueled adventures.

Because she no longer drives, Nordberg pedals to her neighborhood trails in the foothills west of Denver when she wants to go for a ride. There are a few times, though, when an assist from other riders comes in handy.

When she encounters a particularly tricky section of a trail — for instance, a rock staircase with jagged boulders that could snag a front wheel and send a rider over a bike’s handlebars — she sometimes asks strangers for guidance. She carries a bright orange strap and politely asks other riders if they could use it to mark the path of least resistance.

Scott Ehresman, Nordberg’s best friend and biking buddy, leads her through such sections when they ride together. While Nordberg shows no fear when tackling rock staircases, drops and boulders, Ehresman, who is usually filming the action, constantly frets that she will hurt herself.

But even when she does, it doesn’t stop her from getting back on trails. Ehresman said he has witnessed her riding over narrow bridges and rocky precipices, along knifelike cliff edges where one false move would mean a 2,000-foot fall, through deep powder and avalanche-prone terrain on a ski bike in Colorado’s backcountry.

Ehresman, 42, met Nordberg in the 1990s, when she was his supervisor at UPS. They began car-pooling to work and discussing their hobbies. Nordberg convinced Ehresman, an avid climber and a former member of the U.S. climbing team, to try mountain biking.

“At the beginning, I was terrified,” Ehresman said. “She was going down super-steep dirt hills.”

They began taking trips together three or four times per week — and, as Ehresman’s skills improved, their roles reversed.

“I was getting better and better,” Ehresman said. “At some point, it switched. I ended up coaching her. I started going down stuff she had never done.”

But Nordberg, he said, was fearless.

“She was riding some crazy stuff,” he said. “She took some nasty crashes.”

Nordberg has loved biking for as long as she can remember. Growing up in Buffalo, Minn., about 40 miles northwest of Minneapolis, she purchased her first bike when she was 12, using it for a daily paper route.

“It was one of those Schwinn five-speeds with a banana seat,” she said. “I had my paper route from ages 12 to 17, 365 days a year. It got below zero constantly in the Minnesota winter, but when you’re a kid, weather doesn’t bother you much.”

Nordberg used the money she earned from her paper route to buy a snowmobile when she was 15, then a 10-speed Schwinn when she was 17. She spent all her free time outdoors.

“I’d ride my bike to the lake, swim, build tree houses and go shoot BB guns,” she said. “I was always that girl who liked hanging out with the guys.”

She headed off to St. Cloud State University with dreams of becoming a high school teacher, but there were no jobs to be found after she graduated. A friend convinced Nordberg to move to Snowmass, Colo., where she worked for several years as a housekeeper at a hotel and discovered mountain biking and snowboarding. One day, on a whim, she decided to hit the slopes wearing a nun costume she had from a past Halloween.

“It was just a fun thing to do,” Nordberg said. “I’d wear it playing hockey, too. They called me the holy goalie. When you wear a nun costume snowboarding, people notice you. Some people started calling me Sister Shred.”

The moniker stuck.

But after moving to the Denver area, Nordberg realized there was something amiss with her vision.

“It was my 40th and I was going for an I’m-not-old birthday ride,” she said. “I looked at a sign and it was a little blurry. I had a bleed in my eye and double vision.”

She visited a dermatologist about a year and a half later, who delivered a diagnosis: Pseudoxanthoma elasticum, a progressive genetic disorder that, for Nordberg, has caused the loss of her eyesight as well as pain and weakness in her legs. In 2012, she had three femoral artery replacement surgeries in a three-month period.

In 2009, Nordberg stopped driving as her vision continued to deteriorate. And after so many surgeries on her legs, she added a pedal-assist electric mountain bike to her garage a couple of years ago. While she doesn’t ride as many death-defying trails, she still loves rolling through jagged rock gardens and shredding powder on her ski bike. On her 60th birthday — clad in her nun costume for the occasion, of course — she jumped over her first tabletop in a bike park.

As long as Ehresman or another one of her riding buddies — who are all male and, in most cases, more than 20 years younger than her — are willing to drive her there and lead the way, she’s still eager to ride any rugged single-track or backcountry snow line. Offering up her own bikes, Nordberg has taught Ehresman’s teenage daughters how to ride. They’ve known her all of their lives as Sister Shred.

“She loves to cheer everyone on,” Ehresman said. “She wants everyone to try things they maybe don’t think they can do.”

Although she might not shred quite as much as she used to, Nordberg still embraces the small wins.

“You know that feeling of victory?” she said. “I still crave that. You have to do what you can and not be upset about what you can’t do. I’ve had more adventure in my life than a lot of people.”