Settling Issues
At first, Minos hadn't planned to send Lee and Alison on such a mission to the Snow Kingdom. Instead, he would do this travel himself sometime in the future to settle business matters related to beast tamers' techniques and the purchase of beasts for his army.
The Black Plain Army had a small number of beasts to transport groups of soldiers and the resources from the Dry City. In fact, almost all the beasts that his organization had were beings bought from the local citizens.
After all, it was not easy to buy many beasts without drawing the attention of the regional powers since the transport would be very flashy. As such, young Stuart had to be satisfied with the beasts that were in Dry City, beings of low level and weak lineages...
Consequently, his army had few mounts for the soldiers, and most of them were below the 4th stage.