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 Buildings and their special bonuses

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. Also, Grail can be built in an allied town, which can be helpful if you don't have your own Tower or Conflux. All unique Grail building features will be effective for allies (except Castle, Rampart and Necropolis buildings).

Town	Picture	Name	Effect	Notes
		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.
		Spirit Guardian	Increases all owners heroes' luck by 2.
		Skyship	• Reveals the entire map for the player who owns it • Increases the spell points of the defending hero by 150, replenishing immediately after the battle.	Does not cancel out Cover of Darkness.
		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.
		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.
		Guardian of Earth	Increases spell power skill of the defending hero by 12.
		Warlords' Monument	Increases the Attack of the defending hero by 20.
		Carnivorous Plant	Increases the Attack and Defense of the defending hero by 10.
		Aurora Borealis	Fills the town's Mage Guild with all spells Allows learning spells up to the level of the currently built Mage Guild only and doesn't allow learning spells that are never available in Conflux.	In earlier versions, any hero that enters the town learns all spells that are in the game, including Titan's Lightning Bolt*, and not considering the Wisdom level. Fixed in the complete edition, Armageddon's Blade patch 2.2 and Shadow of Death patch 3.2.
		Lodestar	Makes any terrain native to all Cove units (No movement penalty, +1 to attack/defense/speed, ability to see and ignore land mines and see quicksand).

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. It is generically useful and should be picked over any defensive or faction-restricted grail buildings available to you if you're looking to end the game. 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: The problem with Inferno's Deity of Fire is that 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's 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.