Heroes 5.5 WarGame Edition - Tactical Edition.

What if a hero removes the artifact, puts it in their inventory, and puts on another one?

Nothing terrible will happen; only the 4th level of the racial skill will be removed. The artifact can remain in the inventory. The main thing is to prevent its repeated use. Selling it can also be allowed, provided that the ultimate ability is also reset.

Hmm, perhaps it would be simpler to make the amulet "disappear" when the ultimate ability is taken (i.e., destroy the amulet), if it is possible to preserve the racial skill at level 4 using scripts.