HoMM3 HD is a mod (add-on) for the game Heroes of Might and Magic 3.

By the way, in version 1.40, I was experimenting with rebuilding the Library to understand how the enabled checkbox works and noticed the following feature with the Library when rebuilding is disabled. For example: 5 Guildhalls are built, but the Library is not. In this case, there is no Town Portal in the 4th Guildhall. If you build the Library the next day, the Town Portal will not be granted as the third spell. However, if you rebuild the 4th Guildhall the next day (rebuilding still doesn't grant the Town Portal), and only then build the Library, the Town Portal may appear. So, it seems that when Library rebuilding is disabled, the spell in the additional Guildhall slot, which the Library provides, depends on rebuilding the Guildhall itself or the current availability of spells in the Guildhall.
Was this intended?