"Once the Aspect of Wisdom, Malthael abandoned heaven after the Worldstone's destruction," his HotS character bio reads. "In secret, he had resolved to end the Eternal Conflict by becoming a Reaper of Souls and eliminating everything affected by demonic corruption, including humanity."
Malthael is a melee assassin hero that excels at dealing with high-health tank heroes, such as Cho'Gall. His kit is centered around a passive ability called Reaper's Mark—his basic attacks afflict non-structure targets with Reaper's Mark for four seconds, which deals damage equal to 2.5 percent of the target's maximum health every second.
For heroic abilities, Malthael has two very cool choices. The first, Tormented Souls, grants 20 armor and continually applies Reaper's Mark to nearby enemies for four seconds. The second, Last Rites, applies a death sentence to an enemy hero that, after two seconds, deals damage equal to 50 percent of the target's missing health. This means it's guaranteed to kill any enemy below 33 percent health, and still does massive damage if not. Even cooler, the ability comes with a repeatable quest that permanently reduces the cooldown of Last Rites every time it kills an enemy hero.
In the time we've spent with Malthael so far, he seems very powerful. He'll be a strong counter-pick to tank-heavy team compositions, but his focus on damage-over-time effects means he'll be weak to ranged enemies who can kite him or quick assassins like Tracer who can dodge his attacks and burst him down—not to mention those lower health targets will reduce the power of Reaper's Mark.
Malthael is available to play right now. From now until June 26, players can earn rewards in both Heroes of the Storm and Diablo III by playing games in HotS with a friend, similar to the Nexus Challenge event last month that unlocked skins in Overwatch.