Emerge [cost] means You may cast this spell by paying [cost] and sacrificing a creature rather than paying its mana cost and If you chose to pay this spells emerge cost, its total cost is reduced by an amount of generic mana equal to the sacrificed creatures converted mana cost." Paying a cards emerge cost follows the rules for paying alternative costs in rules 601.2b and 601.2fh
The mana gain is awesome, only in a five-color deck, you will likely have to use that extra mana as colorless mana and will still need mana in other colors
I wouldnt suggest this for decks with commanders that have a mana value below four, but otherwise, it really strikes a balance between the Ad Nauseam and Sign in Blood effects
That does not mean this card is bad, for it is quite good
However, it doesnt synergize with the +1/+1 counter theme
Potential buyers were able to sign up for the virtual queue/lottery on the product pages for Lorcana: Rise of the Floodborn