Blood Fountain and Broodheart Engine are literal engines for your graveyard, and represent a large card advantage when you recur them
Strategically, Hades is a must-play because he answers game-ending threats like Elsa Spirit of Winter while giving you a respectable 3/6 body on the board
The cards typically searched by Protean Hulk include [c]Karmic Guide[/c], [c]Kiki-Jiki[/c], [c]Mirror Breaker[/c], and [c]Carrion Feeder[/c], which could collectively one-shot the opponent by comboing together
Anyway, the card is also just as important for Zombies as Champion of the Parish is for Humans, especially when you consider that where Humans uses Thalia's Lieutenant to double-dip on counters on turn two, Champion of the Perished can actually combo with Lazotep Reaver to do the same
But it's not all doom and gloom, as much as some demons would like it to be