Mark (who wrote with his pen name Belsebuub) is a British-born author who taught spirituality between 1990 and 2010. With over thirty years of experience in spiritual practice, Belsebuub wrote a number of books on out-of-body experiences and self-knowledge. He withdrew from public life in 2010.

During a spiritual journey spanning decades, Belsebuub went through a path in which (as he explained) the consciousness of a person is transformed and unites with their personal inner Being.

Belsebuub outlined how this spiritual knowledge is the common heritage of all of humanity. For this reason, Belsebuub never profited from his work, which reached many thousands of people. He offered all his articles, videos, and audio recordings free of charge through his website, belsebuub.com. His books were sold at cost by his publisher, Mystical Life Publications, and Belsebuub receives no royalties from their sale.

His work was widely plagiarized on the internet, with over 1600 instances occurring in the space of a few years. This was due to his writing about his own unique experience which was not published elsewhere.

Belsebuub participated in over 70 media interviews over the years, dozens of which are archived on the Belsebuub Interviews channel.