NAF – New artifacts with unique properties.

Yes, it needs two blades.
The point is that both the Blade of Vengeance and the Blade of Revelation are angelic blades. In Heroes 6, these blades belonged to the Seraphs – one blade allows you to resurrect allies, and the other allows you to deal more damage to units that have already killed allied units. In Heroes 5, this ability was divided between the Greydragons and Altgreydragons, while the basic unit does not have the ability to either resurrect or take revenge. That is, we have a basic angelic blade that has not yet decided which branch of development it will follow – as the Archangel's Blade or as the Seraph's Blade. By influencing it with certain components, we turn it either into the Blade of Revelation or the Blade of Vengeance, giving it a complete, final form.