Of the seven continents the only two close to being "mostly desert", with the definition of desert as an area of limited rainfall and, hence, little vegetation, are Australasia and Antarctica.
There are no continents that do not have deserts. Even Europe has a small patch of desert in Spain - Las Tabernas Desert - and almost the entire continent of Antarctica is a desert.
All continents have desert biomes, even Europe.
South America and Australia
During the Permian, all the continents were joined together in the supercontinent Pangaea, which was covered mostly by desert.
Egypt is mostly in Africa and has a small part in Asia.
Europe and Asia are the two continents located mostly in the northern and eastern hemispheres. The boundary between the two continents is not clearly defined, but they are traditionally considered separate continents due to historical and cultural differences.
All continents have deserts, including Europe which has some small desert areas.
the Sahara desert
none! There is ocean between the 2 continents
Two: North America and South America.
There is no Sierra Desert. If you are referring to the Sahara Desert, it is in Africa.