Grail

The Grail is an item similar to an artifact in the sense that heroes can carry it and exchange it between them in the same way as artifacts. Also it can be sold for 1 unit of any resource. In fact, the Grail is sometimes unofficially referred to as the ultimate artifact. The Grail is typically hidden somewhere in the ground of adventure map, and finding it requires digging it with a hero. Recovering the Grail artifact and taking it to any town enables the player to build town specific Grail Building.

The primary bonuses of Grail Building for all towns are extra 5000 generation per day and 50% additional creature growth per week (rounded down). The growth bonus applies after all the modifiers: external dwellings and Statue of Legion or its components. Additionally, every town has its own unique bonuses.

Finding the Grail

In order to recover the Grail, a hero must dig it out of the ground. A hero without empty slots in a backpack cannot dig. Digging demands the whole amount of a hero's movement points so it is impossible to dig at the same day when a hero crossed even just one tile on the map without tinkering with fast/slow units in the hero's army. Only one Grail may be hidden in the adventure map. However, it is also possible for a mapmaker to set any number of heroes and towns to carry the Grail in their backpack or have their Grail structure built, respectively. When the Grail is buried into the ground, clues to its location can be found at obelisks. Every visited obelisk reveals a part of the puzzle map, which shows the location of the Grail marked with X. Typically the X becomes visible when the entire puzzle map is revealed, but occasionally it will be shown before the last obelisk is visited. However, it is often possible to guess roughly the area where the Grail might lie, and systematically start digging it. In fact, the AI at hard difficulty levels starts digging the Grail even if only a third of the puzzle map is completed.

If the hero carrying the Grail retreats, surrenders or is defeated in battle, the Grail is lost forever. But when he is dismissed, it is possible to find him in a tavern with a Grail in his backpack.

The Grail can be sold to artifact merchants for 1 of any resource.

If the map has no obelisks, it is completely impossible to find the grail (even if every single block on the map is dug on). Also, using "nwcoracle", a cheat that reveals the puzzle map, will have no effect and the puzzle will not show anything.

Grail marker

The Grail can be placed in the map editor to always appear at a specific position. The editor will not allow it to be placed at less than nine tiles away from the edges of the map. It is also not possible to place the Grail in the open like the other artifacts, only its burial spot. Although it can be placed in the backpack of a hero (including one in a Prison or Camp), the Grail cannot normally be set as a reward for a Seer's Hut quest, event, or Pandora's Box. These restrictions can be worked around by hex editing.

Grail Buildings

Buildings
Halls
Village Hall
Town Hall
City Hall
Capitol
Fortifications
Fort
Citadel
Castle
Common
Blacksmith
Mage Guild
Marketplace
Resource Silo
Tavern
Specific
Artifact Merchants
Shipyard
Horde buildings
Grail buildings
Towns

When the Grail is taken to a town and the visiting hero with the Grail "visits" the Town Hall (Village Hall/Town Hall/City Hall/Capitol), a town-specific Grail Building will be built. It can be the second town building per turn, but nothing can be built on the same day after it. The Grail can be built in an allied town, which can be greatly beneficial if the player chooses to construct it in an allied Tower or Conflux town. The effects of Grail buildings are gained by allies (except Castle, Rampart and Necropolis buildings) where applicable.

Town	Grail	Effect	Notes
Castle	Colossus	Increases the Morale of all of the owner's heroes by 2.	Although the documentation states that it increases all allied heroes’ morale, this appears to be wrong.
Rampart	Spirit Guardian	Increases the Luck of all of the owner's heroes by 2.
Tower	Skyship	Reveals the entire map for the player who owns it. Increases the spell points of the defending hero by 150 and replenishes them immediately after the battle.	Does not cancel out Cover of Darkness.
Media:Adventure Map Inferno capitol (HotA).webpMedia:Adventure Map Inferno capitol.webp Inferno	Deity of Fire	Causes every week to be The Week of Imp (+15 Imp / Familiar growth).	External dwellings are not affected by this special week.
Necropolis	Soul Prison	Increases the Necromancy skill of all the owners’ heroes by 20%.	Although the documentation states that it increases all allied heroes’ Necromancy skill, this appears to be wrong.
Dungeon	Guardian of Earth	Increases the Spell Power of the defending hero by 12.
Stronghold	Warlords' Monument	Increases the Attack of the defending hero by 20.
Media:Adventure Map Fortress capitol (HotA).webpMedia:Adventure Map Fortress capitol.webp Fortress	Carnivorous Plant	Increases the Attack and Defense of the defending hero by 10.
Conflux	Aurora Borealis	Fills the town's Mage Guild with all spells up to the level of the currently built Mage Guild, but does not include spells that are never available for Conflux. Fills the town's Mage Guild with all spells.	In earlier versions, any hero that entered the town learned all spells that were in the game, including Titan's Lightning Bolt*, regardless of their level of Wisdom. Fixed in Armageddon's Blade patch 2.2, The Shadow of Death patch 3.2, and Heroes of Might and Magic III: Complete patch 4.0.
Cove	Lodestar	Makes any terrain native to all (allied or enemy) Cove units: No movement penalty +1 to attack/defense/speed Can see and ignore land mines and see quicksand)
Media:Adventure Map Factory capitol.webp Factory	Lightning Rod	Strikes all enemies with lightning at the first round of every battle. Damage is based on town building count. Damage formula is 35 + n × 7 where n is the number of built buildings (upgrades do not count separately) up to a maximum of 168.	Effect happens on the first round of the controller's turn, not the first round of combat. Does not affect creatures immune to Chain Lightning. Deals reduced damage to creatures with Spell damage reduction. Damage is increased by Sorcery and Orb of the Firmament, but not by Air Magic nor Magic Clouds. Ignores Anti-Magic, Cursed Ground, Interference and anti-magical artifacts (e.g. Orb of Inhibition).
Bulwark	Spirits of the Forebears	Increases the Defense of the defending hero by 20.

Gallery

• 
  Spirit Guardian concept
• 
  Guardian of Earth concept
• Airships were a modified Skyship design (see left)
  (Beyond the Horizon  prologue)

User Commentary

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• Castle: One of the less impactful grails, which is often made redundant by Knights’ Leadership skill. The bonus can be seen as Advanced Leadership without needing to waste a skill slot.
• Rampart: Similar to the Castle grail, but even less impactful.
• Tower: Having this building gives a massive tactical advantage, and any player will be perfectly able to spot any attempt of siege or attack not only to this town but to all friendly heroes and buildings.
• Inferno: Typically grail buildings are built long after the imps, low tier creatures, are useful. However, the scrupulous Inferno player can turn this into an incredibly powerful advantage. A high level Marius equipped with any of the extra hitpoint artifacts can turn these extra imps into more demons with pit lords. A vial of lifeblood makes conversion 50% more efficient, requiring six imps per demon as opposed to nine. This means with the addition of the grail, birthing pools and castle, one can expect an additional 11 demons per week.
• Necropolis: Typically grail buildings will be acquired long after skeletons have already been farmed from neutral encounters, but the 20% boost is still appreciated for whatever fights there are. It is also completely worthless for non-Necro opponents, which is nice. Notably, this is the only source of Necromancy that wasn't halved in Horn of the Abyss, making the boost even more significant.
• Dungeon: Having a +12 Spell Power boost together with 5 level of Mage Guild allows to cast tremendous spells like Chain Lightning or Implosion dealing horrific damage, or to make essential spells like Slow, Haste, Bless or Curse everlasting.
• Stronghold: This bonus gives an absurd damage bonus, able to increase the damage output of even the highest leveled creatures by about 50%, any hero holding a town with this building is nearly unbeatable except by an overwhelming army or an opposing hero with a very high level.
• Fortress: This boost is considered to be the best in terms of siege defense, not only does it make all units tanky but also gives them a powerful damage steroid, this is particularly useful for the Fortress creatures, who have somewhat low stats (but extremely powerful and annoying abilities) and allows them to achieve a powerful combination of destruction, tankiness and annoyingness.
• Conflux: Arguably the best Grail building. Having guaranteed access to Town Portal, Dimension Door, and Fly by itself is already incredible. Getting every single other spell is just bonus. Even with the nerfs in Horn of the Abyss, this Grail is still the most powerful.
• Cove: Effectively provides a global buff to all Cove units while preventing movement penalty with mono-Cove armies. The speed is particularly appreciated given how sluggish most Cove units are.
• Factory: Probably in top 3 best Grail buildings. Lightning Rod is global, not in-town only. It can clear most neutral creatures (especially if they are split in 7 stacks) for free and take a dent out of the opponent's army. The damage scales primarily from town building count (7 damage per building, starting from 42 with just Village Hall and Lightning Rod up to 168 when fully built), so it is best built in your main town. See Arrow tower#Damage calculation to see how the damage works. If you send multiple heroes against the opponent one by one, assuming the opponent has 7 creature stacks, they will deal up to 1176 damage for 2500 gold each. With a large gold supply, this can be used until the enemy army is depleted, as long as the enemy is accessible in a day (1500-1700 movement points) from any of your towns or a Tavern. Keep in mind that the effect does not happen until your turn, meaning the opponent will have a chance to cast a protecting spell on their troops if they have a faster creature; it doesn't work on units immune to Lightning Bolt and Chain Lightning (e.g Gold and Black Dragons) and works very poorly on Golems.
• Bulwark: Combined with Bulwark's already high defense on their heroes and high health units, this will make defending creatures nearly unkillable unless facing an overwhelming army.

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