Haven faction discussion.

But then, why give a sword? It would have been better to give a pendant or a cross with a blue gemstone in the middle for resurrection.

Obviously, they gave a sword for aesthetic reasons, and a cross, like the ones monks wear, wouldn't fit the animation, I think. Besides, archangels used swords to resurrect in Heroes of Might and Magic V, so the developers just expanded on that and probably gave two swords for two purposes.