MrStabby wrote:They're all listed under order so I figured they're still able to be used. I might be wrong.
You are not wrong. You're able to take allied units as part of your army, and they don't necessarily have to be from one list.
However with that said..., Idoneth are an army that really benefits from a focused approach.
Do you want Akhelian Cavalry? A Namarti Horde? A balanced mixture? The characters in the army really tend to be 'built' to buff one playstyle over the other, with certain Enclaves further cementing your choice.