The Devil's true form resides in Hell; what was obliterated was merely its thought descending upon the Mortal World, along with its earthly vessel.
The Devil is not truly dead. However, it spread too many thoughts when it descended to the Mortal World, suffering devastating losses that greatly weakened Hell's power. Those familiar with Hell's ways know the consequences: this Devil has lost the ability to defend its territory—the outcome is self-evident.
The Death Knight understands fairness. Knowing too well that it's better to have less rather than endure unequal distribution, he brings equality. He won't let just one Devil suffer misfortune; he hunts down the others.
"..." x3
The Three Overlords exchanged bewildered glances, and Setoras was the first to break: "Why are you all looking at me? You two also have keys. Hurry up and give the orders!"
Why give orders? Their lives and deaths have nothing to do with me. Just because we formed an alliance? x2