We know a lot about Mongols.
Muslims see it as the dark chapter in their history- destruction of Baghdad, destruction of the libraries and Muslim civilization, destruction of Samarkand, Basra, and many other great cities of Persia and present day Afghanistan. Never ending hordes of horses. Barbaric warriors that would not stop for rest and meal and when thirsty would stab a horse and drink its blood. Inhuman humans, who would butcher even women and children and then would compete with skull mountains!
Europeans see Mongols as a powerful force that knocked at the door steps of Europe. A military power that took over Eastern European states. A power that could not be defeated.