ToE H5/HoF
Magic Guild level one
Magic Guild level one Cost Requirements Magic Guild level one
  • 2000
  • 5
  • 5
Town Level 3
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.
Pillar of Bones
Pillar of Bones Cost Requirements Pillar of Bones
  • 1000
  • 10
Town Level 6
Magic Guild level one
Effect
Adds 10% to Necromancy skill of all Necromancers under player's control and grants them additional 150 points of Dark Energy (cumulative by all cities), i.e. supports Necromancy special ability.
Shrine of the Netherworld
Shrine of the Netherworld Cost Requirements Shrine of the Netherworld
  • 1000
  • 5
Town Level 9
Effect
Provides -2 morale penalty for attacking enemy, allows transformation to undead troops (according to creature tier, if corresponding dwelling is built in this city).
Unearthed Graves
Unearthed Graves Cost Requirements Unearthed Graves
  • 500
  • 5
Town Level 6
Graveyard
Effect
Boosts skeleton, skeleton Archer and Skeleton Warrior growth by +6 per week.
Dragon Tombstone
Dragon Tombstone Cost Requirements Dragon Tombstone
  • 3000
  • 10
  • 10
Town Level 15
Dragon Graveyard
Effect
Boosts Bone Dragon, Spectral Dragon and Ghost Dragon growth by +1 per week.
Tomb of the Lost
Tomb of the Lost Cost Requirements Tomb of the Lost
Effect
The Tomb of the Lost provides extra gold income (+5000 Gold per day), extra creature growth (+50%), boosts the Necromancy skill of all the player's heroes by 50% and provides them with additional 150 points of Dark Energy. A Tear of Asha is required to build this structure.
Expert's Corner (by ThE_HyDrA)

Necropolis' abundance of special buildings help to strengthen their relatively weak creature statistics. The Necromancy Amplifier is another bonus that aids the Necromancy skill, which can result in a throng of skeletons within the first few weeks. Its expensive sulfur cost does not endear people to it, though thankfully, sulfur is only required with the Lich's Mausoleums and Unearthed Graves, making a total cost of 25 (aside from Mage Guilds), which is easily affordable.

The Shrine of the Netherworld works in a similar way to the undead transformer, except that the creatures are transformed in their level, making it extremely efficient. This may be necessary for spells like death scream and the Lich's area attack not affected your living creatures. You can of course be selective and choose creatures that you feel will benefit you as an undead. It is also good for sieges, so, if you're bracing yourself for one, and you don't yet have this building, it may just help to swing the tide in your favour.

The Unearthed Graves are another welcome bonus to the Skeletons' already burgeoning population thanks in part to Necromancy. Chilling Steel and Toughness work well with your skeleton archer legion, so this building will only serve to strengthen that power. The Dragon Graveyard is a much needed structure, enabling your level 7s to compete with other like-leveled creatures from the other towns. It is no secret that Spectral Dragons are drastically weaker than their Black or Emerald cousins, but this structure can help to equalise that defecit. The price is not much, and the pre-requisite is nothing when compared to the town level you need simply to recruit Bone Dragons.

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!