The difference of offline play in Heroes II and Heroes III.

Secondly, in Heroes of Might and Magic II, it is precisely an artifact. An attribute of the hero that affects his characteristics. The exception is the Golden Goose, which does not affect the hero. However, in Heroes of Might and Magic III, the Grail is more like the Goose. It adds a number of bonuses rather to the player as a whole than to a specific hero. The Grail in Heroes of Might and Magic III is more like an artifact for the city. Moreover, its static nature (since it cannot be moved from city to city) makes it a kind of mixture of a special building, a city artifact, and something else. It is somewhat similar to a hero stationed in a garrison with eight units in the field (that is, with no chance of leaving the city), with a legion statue, and something else...
The only difference between the UA and other artifacts in Heroes of Might and Magic II is that it cannot be captured by the enemy. When a hero with the UA is defeated, the UA mysteriously disappears...