The mana value of a converted permanent on the battlefield is equal to the mana value of the card's front face, no matter which face is up
You wont be as incentivized to play the remaining enchantment removal like Seal Away and Ixalans Binding with Cleansing Nova in your deck, but theres no harm in having the versatility to destroy all artifacts and enchantments as well if thats necessary
Finally, the level three of this card, which only costs an additional one mana to activate, gives all creature cards in your graveyard sneak with a cost of four mana
The deck starts by playing a number of efficiently costed vampires with strong secondary abilities including drain (Astarion, Defiant Bloodlord, Sanctum Seaker), mass reanimate (Bringer), card draw (Champion of Dusk, Crossway Troublemakers, Dusk Legion Duelist), granting your army lifelink/deathtouch (Crossway Troublemakers), +1/+1 counters (Drana), anthem effects (Edgar), creature tokens (Mavren, Preacher, Sanguine Evangelist), Explore (Amalia), removal (Vona), and many many more