The MdS is an annual event that started over 20 years ago. The race covers more than 150 miles across the Sahara desert, run in stages over 6-7 days  - equivalent to 5 1/2 regular marathons.

To add to the experience, competitors have to carry everything they will need for the entire week, apart from a tent (that means food and a way of cooking it, clothes, medical kit, sleeping bag etc). Water is rationed and handed out at each checkpoint. Mid-day temperatures are expected to exceed 40°C, as competitors cross uneven rocky, stony ground as well as 15 - 20% of the distance being in sand dunes.

The heat, distance and rubbing will trash your feet and may cause severe trauma if incorrect shoes and equipment are used. Mental stamina probably constitutes at least 50% of whether people finish.
To cap it all off, there is a double marathon stage mid-week, which few people complete before dark that evening and some will not come in till after dark the next night. This is followed by the 42km Marathon stage!! Fun, fun, fun!!