They never had a really coherent theme, but Captain N'ghathrod brings them together as mill machines, resurrecting what is then put into the graveyard
That versatility makes it great for saga decks - a type of enchantment that hadn't been invented when Power Conduit came out
Hopefully, the seal and design will be corrected to improve on the faults of the first
You can certainly run this Balrog as your commander and do Dargo tricks, but I think it works just fine as a card in your 99 and played fairly, especially if you have ways to bring creatures back from the graveyard
This is also a board wipe that hits all nonland permanents, so theres a good chance this card will take care of whatever form your opponents threat is taking
Easy Prey is an excellent example of this, like Void Beckoner before it