Hi, navidsalar. "Veritable host" in this language means "a real/genuine army." Although this gathering of Ghazi's kin wouldn't be large enough to qualify as "an army" in some other place, the gathering was large enough to be considered an army by Bedouin standards.
[ usually: ~ + of] a great number of persons or things;
multitude:a host of details.
being truly or very much so;
It means that though it was just a gathering of his kin, by Bedouin standards, it could very much be called a large group/ a large force. It implies that it was uncommon to find a large group of Bedouins.