As a four-mana aura, its good that you can technically use it in a fair way, slapping it onto something as a response opponents removing a different creature (or wiping the board)
As before, Vampire Kingdom boosts both sides, cancelling out the difference
Both of these pair nicely with a spare Level 6 to make Red-Eyes Zombie Dragon Lord, as redundancy for Mercurium, its effect less relevant than being a Level 10 Zombie Synchro
Its not flashy, but in slower or more Voltron-oriented builds, protecting an important piece with this enchantment can be exactly what you need
Mithril Coat solves this issue, letting it be played at Flash speed and be auto-equipped to a legendary creature
These alternate-art Leaders feature full-art illustrations and are highly sought after by collectors