Resonator
Auto-translated
If we disregard the Necropolis King's cloak (which is banned in competitive play), then the Angel Alliance is the best artifact. It provides a ton of stats, which can even turn a Barbarian Mage into a powerful unit, Expert Prayer (which a Barbarian Warrior can't even have because they can't learn water magic), and the ability to recruit creatures from different cities without lowering morale (which is great on random, large maps) – all of this makes it the best artifact overall.