Some kingdoms have a special relationship with mythical creatures. This is the case of the Kingdom of Caledor, that can wake up powerful dragons and lead them into battle. Also the Kingdom of Yvresse traditionally count with the mighty Griffons. Not so powerful as dragons but higher in numbers.
Some other Kingdoms such Avelorn, Chrace of Saphery keep an ancient alliance with the Great Eagles of the Annulii. However not only the Asuryan followers can go to the battlefield mounted on these beasts. The kingdom of Nagarythe have tamed terrible Manticores and raised Black Dragons mutated by the chaos powers. Make sure of having a couple of bolt throwers before start a battle, or your enemies will prevail.