Heroes 5.5 WarGame Edition - Tactical Edition.

The amulet can provide an additional +2 attack (i.e., I didn't finish writing it, +0/+2/+4/+6)
The point of the amulet isn't how much it enhances the racial skill, but that it grants level 4 in the skill, opening up the possibility to learn 4 perks and thus, Special Abilities.

Has the issue of what happens to the mastery amulet after obtaining Special Abilities been resolved? If we get the amulet, we get the fourth level in the racial skill, after which we can upgrade Special Abilities, and the amulet can be safely passed on to another hero and the same can be done – this is nonsense, because then you can upgrade Special Abilities for all heroes, and I think it should be done so that when the 4th level is reached in the racial skill, the amulet disappears immediately.