From Halopedia, the Halo wiki
Drekars are sleek vessels that combine Covenant technology with Jiralhanae construction methods. They are equipped with stealth systems.
Drekars were commissioned personally by the Prophet of Truth prior to the outset of the Great Schism. They served a place in his plans for the removal of the Sangheili from the core military castes of the Covenant to be replaced by the Jiralhanae, and as such combine the technological advances of the Covenant with Brute construction and design methodologies. Following the onset of the Schism and the collapse of the empire, an unknown number of these ships were nearing the final stages of completion - and in the years following would slowly fall into the hands of Atriox in a number of clandestine raids launched by the Banished against informant cells and former-Covenant armories.
Drekars fill a role in the Covenant and Banished fleet most analogous to the prowlers employed by the UNSC Navy. Drekars were most notably employed by the Banished in the months leading up to the Battle over Installation 07 - with the stealth ships used to influence the shift of events leading up to the Banished occupation of the ring. How many drekars the Banished operate remains unknown.