Create your own artifacts! — New ideas.

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Set of construction tools.
A hero with this artifact can participate in construction in a town, spending all their strength on the second building for the day.
(all versions)

Super Sleep Wand.
Allows you to temporarily incapacitate an enemy hero in battle, removing all the bonuses they provide to the army and the ability to cast spells. This is achieved through a special spell that costs 30 mana + 2 * (enemy's mana). The duration depends on the hero's magic power divided by 2.

Ship wheels

Allows you to upgrade one ship so that it can sail on the sea and travel on land. However, disembarking from such a ship still costs 1 turn. The ship can also be destroyed and captured by the enemy. Such a ship cannot enter a town or attack it.

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XEL

Sphere of Absolute Power. Relic. Grants the hero a level upon first placement in the inventory, provides significant bonuses to all stats, and allows the hero to enthrall enemy creatures. If the hero possesses more than one Sphere, the effect increases by a factor equal to the number of Spheres.

Interesting

Added 3 minutes ago

Tengro

Nicholas' Blade. Artifact for the Knight. Allows retraining +10 warriors per week in each city, but -1 to morale. For others, +1 to attack.
Book of Sphere Magic. Artifact for the Mage. Allows casting twice per turn at double the mana cost, but -1 to spell power. For others, +1 to knowledge.
Elven Arrow. Artifact for the Elf. Allows archers to counterattack with an arrow, but -1 to initiative. For others, +1 to archer damage.
Urghash's Key. Demon artifact. Increases summoning from the gate by 25% and increases the number of summoners by 25%. But -1 to speed. For others, +1 to attack.
Ashes' Poison. Artifact for the Necromancer. +25% dark energy, -1 to attack.
For others, +1 to the damage of all creatures.
Hill Sign. Artifact for the Dwarf. Reduces the cost of runes by 1.5 times. But -1 to speed. For others, +2 to defense.
Banner of the Liberator. Orc artifact. +50 rage at the start of the battle, +1 to morale, -1 to speed. For others, +2 to morale.
All effects apply to "others."

I agree with many points, especially I liked Urghash's Key and the Banner of the Liberator.