Many law-firm founders reach a certain age and start to wonder how they want to spend the rest of their career.

For Per Magnusson, an attorney well-known across Europe who turned 60 last year, the answer was to do it all over again: start from scratch, with a twist, and see what happens.

His new venture, Magnusson Minds, opened for business March 1 in Stockholm. The firm, which offers a range of advisory services, has a full-time professional staff of one—Magnusson—and clients ranging from corporations to boards of directors to law firms, on matters ranging from litigation and arbitration to mergers and acquisitions and strategic planning.

On paper, it is a far cry from Magnusson, the law firm he founded in 2004 in Stockholm and built into a regional presence, with some 200 lawyers in seven countries in Scandinavia and the Baltics, before gradually turning it over to his partners over the past two years.

Known for cross-border expertise and being early to embrace legal tech and diversity, the Magnusson firm has won numerous professional recognitions, including being named European Firm of the Year by the British Legal Awards three years in a row, from 2012 to 2014.

"There are many law firms but very few law-firm entrepreneurs," Magnusson said Friday by telephone from Stockholm. Before founding his former firm, he had started another law firm in 1991, which he eventually merged with a larger competitor.

"For years I had been accustomed to running law firms, developing them, being responsible for big organizations," he said. "This is a chance to do something a little different."

A self-styled "trusted advisor," Magnusson Minds aspires to be a one-stop portal for professional advice. Magnusson provides the legal part, drawing on more than 30 years of practice. He calls in specialists in other disciplines—accounting, management consultancy, forensic investigation—as needed.

"We are regulated by the Swedish bar, so the firm itself is limited to providing legal advice to clients," he said. "But it depends on how you define advice. Offering strategic business advice is part of an experienced lawyer's daily work."

Like many startups, Magnusson Minds is a family business. Magnusson's wife handles office management and administration; his daughter, a designer, created the logo and is building the website. Magnusson has a home office but he can work from anywhere—not much of a change, he said, from his former routine.

"As far back as I can remember, I have worked from everywhere—the gym, the beach, a sunbed," he said. "The line between work and not-work has always been very blurry for me."

As of Friday, Sweden had not imposed restrictions on mobility to battle the COVID-19 crisis. Shops, restaurants and gyms were still open. Magnusson, who is staying close to home nonetheless, said he was not surprised.

"The Swedish way of doing things is not to tell people what to do," he said. "It's to suggest what they should do."