ToE H5/HoF
Magic Guild level one
Magic Guild level one Cost Requirements Magic Guild level one
  • 2000
  • 5
  • 5
Town Level 3
Village Hall
Effect
Allows a visiting hero to learn the spells kept within. Keeps 3 spells of the first circle.
Magic Guild level two
Magic Guild level two Cost Requirements Magic Guild level two
  • 1000
  • 5
  • 5
  • 1
  • 1
  • 1
  • 1
Town Level 3
Magic Guild level one
Effect
An upgrade of the Magic Guild level one.
Allows a visiting hero to learn the spells kept within. Adds 3 spells of the second circle.
Magic Guild level three
Magic Guild level three Cost Requirements Magic Guild level three
  • 1000
  • 5
  • 5
  • 2
  • 2
  • 2
  • 2
Town Level 3
Magic Guild level two
Effect
An upgrade of the Magic Guild level two.
Allows a visiting hero to learn the spells kept within. Adds 3 spells of the third circle.
Magic Guild level four
Magic Guild level four Cost Requirements Magic Guild level four
  • 1000
  • 5
  • 5
  • 3
  • 3
  • 3
  • 3
Town Level 3
Magic Guild level three
Effect
An upgrade of the Magic Guild level three.
Allows a visiting hero to learn the spells kept within. Adds 2 spells of the fourth circle.
Magic Guild level five
Magic Guild level five Cost Requirements Magic Guild level five
  • 1000
  • 5
  • 5
  • 5
  • 5
  • 5
  • 5
Town Level 3
Magic Guild level four
Effect
An upgrade of the Magic Guild level four.
Allows a visiting hero to learn the spells kept within. Adds 2 spells of the fifth circle.
Library
Library Cost Requirements Library
  • 3000
  • 2
  • 2
  • 2
  • 2
Town Level 9
Mage Tower, Magic Guild level one
Effect
Reveals 1 extra spell in each circle of Magic Guild.
Arcane Forge
Arcane Forge Cost Requirements Arcane Forge
  • 2000
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
Town Level 3
Effect
Allows forging equipment for creatures (i.e. supports Artificier special ability).
Artifact Merchant
Artifact Merchant Cost Requirements Artifact Merchant
  • 5000
  • 5
Town Level 6
Marketplace
Effect
Sells artifacts.
Treasure Cave
Treasure Cave Cost Requirements Treasure Cave
  • 3000
Town Level 12
Altar of Wishes
Effect
Boosts Djinn, Djinn Sultan and Djinn Vizier growth by +2 per week, provides additional 500 gold per day.
Skyship
Skyship Cost Requirements Skyship
Effect
The Skyship increases weekly creature growth by 50%, provides your empire with additional 5000 gold each day and boosts Knowledge for defending heroes by +10. A Tear of Asha is required to build this structure.
Expert's Corner (by ThE_HyDrA)

Academy's special buildings are based more on enchancements and artifacts that creature growth or inflicting morale penalties. The Library is a structure that can sometimes alleviate the pain of an unfavourable mage guild, and should only be invested in if your magic hero has not lucked into the preferred spells, or you would simply like to extend the range of the mage guild to cater for several magic heroes (which is not uncommon in the Academy and especially so for large maps). However, since it's a requirement for the costly Silver Pavillion, your precious resources need to be in abundance. Cost shouldn't be a problem if precious resources are fairly plentiful, though many of those would have been devoted to upgrading the mage guild and, later, Silver Pavillion if it can be afforded. Waiting until at least the 3rd level in mage guild development is recommended before buying the Library unless it is a smaller map.

The Artifact Merchant, while expensive, is a good resource for artifacts if the map is particularly scarce of these items. This is definitely not a high-priority building and is not required for any of the Academy's other buildings. The Treasure Cave, on the other hand, is an excellent building. Not only does it boost the Genie/Master Genie growth by 2 per week (a massive 66% of its base growth rate), but it also produces an additional 500 gold per day! While it requires the Pinnacle of Wishes and a rather generous Town Level 12, it should be an early investment, especially considering the relative difficulty of keeping Genies on the battlefield thanks to their low Hit Points. This helps to abate the trend, and easily gives you back your gold that you paid - almost paying for itself - and the genies - within 1 week.

This information comes from the Heroes V release version (v3.0).

Thanks to Fiur and Vokial for in-game screenshots.
Thanks to sfidanza for the work on this page.
Thanks to ThE_HyDrA for creating and looking after the Heroes 5 section of Age of Heroes!