On the surface, Eater of Hope is an okay Demon creature. He costs 5BB (5 colorless and 2 Black mana) to cast, and he is a 6/4 flier. The Eater has two abilities: one that activates with a single Black mana that allows you to sacrifice a creature to regenerate the Eater. That’s useful enough, making him more difficult to destroy that most creatures. The Eater's second ability costs 2B (2 colorless and one Black mana) and allows you to sacrifice two creatures to destroy a target creature. While this is not seemingly cost-effective, it's useful in a pinch, especially if you have creatures sitting around doing you little good, anyway.
In Limited (i.e. draft and sealed deck), Eater of Hope is a useful card and could even be considered a “bomb.” A 6/4 flyer that can regenerate just by sacrificing another creature and paying a single Black mana is a fair price to pay. The Eater also has the potential to remove someone else’s “bomb” creature, albeit at a bit of a costly price. Still, with a limited card pool, this is certainly playable.
However, even in Limited, seven mana for a 6/4 flyer is not the most cost-effective creature. Understandably, this isn't a creature you'd see played in Standard, Modern, or other 60-card competitive formats. But, Commander is another story.
In Commander, where infinite sacrifice outlets can be generated, the Eater can actually machine-gun entire boards. There are a number of Commander decks that this Eater can find a home in, a few which are Mono-Black. Endrek Sahr, Master Breeder is a particular good home for Eater of Hope, as there are plenty of Thrull tokens to sacrifice to his abilities.
But the deck that can make the most use of Eater of Hope is Meren of Clan Nel Toth. The highly-popular Meren doesn't always play the Eater, but this Demon works well into Meren's plan of making your things die in order to get experience counters. Those experience counters then allow Meren to bring back bigger and better things from the graveyard. So, the Eater has great synergy with Meren.
Repeatable removal that is on a flying stick that can be regenerated is always good in the Commander environment.
It's just too bad that they didn't go with the name that he was first spoiled with: Devourer of Hope. That reduces this card’s coolness by at least 20 percent...