Share the Spoils is a symmetrical effect in that it gives your opponents access to the value, but it is excellent if youre looking for different answers, or threats to keep the game moving forward
Counters put on Purphoros remain on it while it's not a creature, even if they have no effect
Returning the Elf you control to its owner's hand is the cost to activate the ability
The more likely scenario, however, is that youre going to try to string together some spells early on to spit out eight-to-twelve Goblins and maybe finish your opponent off with Grapeshot if theyre able to stabilize
Black is famous for cards that allow you to pay life to draw cards such as Necropotence and Village Rites, and in Commander you have a lot of life to play with
This ability also gives it a unique chance to show up in Legacy Mississippi River decks