With Heartless Summoning it is much more plausible to evoke and elemental, and pay the WUBRG cost to keep the token around, effectively double spelling
According to Magic the Gathering market website MTG Goldfish, the value of Mana Vault has floated up to the region of $150 to $300 dollars depending on printing, roughly tripling in price
I do have to wonder what Wizards will do if they ever reprint cards like Splinterfright, Revenant, or the many Lhurgoyfs that care about cards in the graveyard
The main strength of this Sapphire Steel deck is its items, and with powerful characters who take advantage of them, it can easily deal with any early game threats and dominate the late game as well
and each other piece has an eyeball on it
But you need a way to leverage that