So essentially he needs to keep participating in kills to become this highly sustainable presence in fights. If you activate this ability he'll heal over a five second period in accordance with how much Essence you've collected. 10 Essence from takedowns on enemy heroes and two from nearby minion deaths. He gains a resource called Essence when enemies die. Here are his abilities: D - Collect Essence

He can also regenerate health and do area of effect damage making him a massive pain in the butt during team fights.

So he's a melee warrior whose high mobility should come in useful for ganking or for setting up pick-off kills. It kind of fits as Dehaka's whole deal is that he stayed home on the Zerg planet and is an individual not part of a swarm but I'm not sure that the Overmind would have ever called him because he doesn't have a psionic connection which I assume you need for zerg brain broadband and booty calls from the Overmind or whatever.

My knowledge of StarCraft lore is perhaps best described as 'minimal' but there's a short Hotline Bling reference in the Dehaka introduction video so now I have 'You used to call me through the Overmind.' stuck in my head as a lyric. Primal Zerg hero Dehaka is burrowing his way into Heroes of the Storm from the StarCraft-iverse to become the game's fiftieth playable character.

Heroes of the storm zerg