[Edi]

This is more Dominions - PPP related than Dom2 related, but is relevant to Dom2 as well if all the sites from PPP are included.

There was a question in the DominionsMagicSites Excel file about the Academy of High Magics possibly having four variants. It does indeed have those variants.

There is one Academy of High Magics for each of the elements, Air, Earth, Fire and Water. They do have some differences in gem income though. These are as follows:

Air: 1 air, 1 death
Earth: 1 earth, 1 nature
Fire: 1 fire, 1 astral
Water: 1 water, 1 blood slave

I have found Water and Earth Academies, so those are accurate, the Fire Academy I lifted from the xls file, which gives the Air Academy the missing two types of gems as income. All get the same two types of recruitable wizards.

Obviously this means that the Water Academy is (at least in my opinion) the most desirable one, because free blood slaves are after all free blood slaves, and you don't get those too often.

Edi