So Thanos has been keeping Mephisto around throughout the series so far, but it’s not clear why. Thanos is omnipotent–he clearly doesn’t need Mephisto. But he seems to enjoy company. Flattery. His ego is his biggest vulnerability. Finally, in issue #4, Mephisto can’t keep himself from being himself–a trickster and a devil. So he whispers in Thanos’ ear and convinces him to make himself vulnerable, so he’ll appear more tempting to Death.
But even in his weakened state, Thanos kills all The Avengers. Dead. And then we see that Adam Warlock has been holding back his troops for something bigger…
Eternity is coming to kick Thanos’ ass.
Cosmic comics have never been better than this.