NAF – New artifacts with unique properties.

You could add the golden goose from the second game.)))
Here are some ideas for artifacts:
1)Holy Water. Initiative of all undead creatures -20%, when casting the "Holy Word" spell, magic +10, prevents casting "Unholy Word".
2) Ribbon of the Messenger. Reduces the aggression of monsters, allows you to exchange it for 1 building in any city for free.