Atlantean Warbirds
A proud Atlantean tradition, the art of riding Aetókós - the giant birds of Atlantis, has until now not been utilized in warfare, as history had been kind to the people of Atlantis, but troubled times are ahead. Known for it's magnificent stature and lightning fast speed - the giant herbivorous bird has pronounced sexual dimorphism, with males being 2.4 meters high and 300 kg heavy on average, and females 3.6 meters high and 840 kg heavy on average. Bluish and hair-like feathers cover most of the body plus a small portion of the neck below the head. In relation to its body, the head is small with a pointed, sharp and somewhat curved beak from a predatory ancestor, but the bird's main weapon are it's feet, which are large, powerful and feature enlarged raptorial claws used for slashing when simply kicking doesn't suffice. A prominent feature is a long neck that allows the bird to reach tall vegetation.
To militarize the birds, a breeding program is established so as to create birds specifically grown for combat - trained to be faster, more endurant and more obedient than the average Aetókós by a rider since youth. The prestigious warbirds would then be armored and sent out to perform the role of heavy cavalry - armored to protect them from any arrows they might face. Charging at enemies at high speed, the warbirds would be capable of jumping inside formations, breaking them up from the inside and kicking troops with the full force of a 1 ton bird, without even getting into it's sharp foot-long talon.
This is estimated to be at least an expense level cheaper than the Tromousavra due to being a herbivore, and would give us a faster form of cavalry that we could use in groups instead of solitary units, as well as in conjunction with our other troops as opposed to utilizing them as terror weapons capable of causing grievous friendly deaths.