Harbinger, Sovereign, Leviathan

The three drakes of the Ebon Onslaught serve as one of their most powerful airborne weapons. An embodiment of the paths of runes that the death knights are capable of unleashing. Each drake has runes grafted to their armor, allowing the Ebon Onslaught to recharge their runes on the field. However, it is costly to maintain these drakes, putting a huge drain on resources. The majority of times, these drakes are put to slumber within the Hold, only to be unleashed for major battles.
They serve as anti-infantry weapons for the Onslaught, as well as a demoralizing effect with their roars filling the sky for all the living to hear.

Harbinger, the Wrath of the Onslaught.

The Unholy Drake. Bound by saronite plates to hold its decaying flesh and plague bile breath, it serves as the primary anti-infantry force. Captured in Northrend, this proto-drake was corrupted and turned into a weapon by the Onslaught.

Sovereign, the Burning Blood Wyrm.

The Blood Drake. Killed by the Harbinger, the red drake would be raised as the primary guard for the plague drake, capable of taking massive amounts of damage and unleashing its own burning blood breath as a weapon.

Leviathan, the Black Ice Blizzard Wyrm.

The Frost Drake. Killed by the Onslaught, this blue drake was raised into the secondary guard for the Harbinger. While capable of anti-infantry attacks, its primary target is that of mages, blinding and dampening magic with its black ice breath.
Sovereign and Leviathan were both sacrificed to aid the Onslaught during a campaign in Desolace, leaving Harbinger as the sole drake left under the command of the death knights.