A khalasar is a nomadic horde of Dothraki led by a chief known as a khal. Khalasars range in size, and can be anywhere in the hundreds to the tens of thousands: Khal Drogo once led an enormous khalasar of forty thousand. These hordes generally wander out Essos, looking for glory or simply travelling. On occassion, they will fight other khalasars, but very rarely. It is said that facing a large khalasar on the open field of battle is suicide for any kind of army, even Westerosi hosts.