I confess, the reason I wanted to write this post comes from the fact that when I was writing the recent Warriors in Lore post, I went to link to our Grom Hellscream article and found that it didn't exist. "Seriously," I asked myself, "we don't have a Grom Hellscream post?" I just assumed we'd written one. Why wouldn't we have written one? (We also don't have an Orgrim Doomhammer one. I plan to fix that.)
So then, what do we know about the Giant's Heart? (Grommash, his given name, means "giant's heart" in Orcish; it seems like a fitting title.) We know that he was born in what was then still Draenor during the period before the rise of Ner'zhul and later Gul'dan to their respective heights as masters of the orcish people and creators of the Old Horde. It is not known how Grommash gained his position as chief of the Warsong. He didn't directly inherit it, and the other chieftains suspected him of somehow gaining the position through foul play, but none of them could dispute his fitness to rule nor the loyalty of his people. However, he became their leader; lead them, he did.
When Ner'zhul came to the orc chieftains with the suspicions that led them to war with the draenei, Grom simultaneously distrusted the old shaman motives yet embraced the conflict, seeing in it a means to prove his own prowess. Grom's distrust of Ner'zul sprang from his contrary nature. As both Ner'zhul and his successor Gul'dan would learn, Grom Hellscream proved extremely resistant to direct instructions. Even when Blackhand the Destroyer became Warchief (a position resurrected and altered by Gul'dan to make the orcish forces more amenable to centralized control), Grommash often did exactly what he wanted to do and ignored his supposed leader and his commands. Grom would only take orders when they exactly suited what he intended to do, anyway.
Still, while he had his suspicions, Grommash Hellscream was not troubled by the war with the draenei the way Doomhammer or Durotan were. He held them in no regard and in fact saw them as a perfect way to increase his own prestige among the clans. In truth, even that might have been a subterfuge. Grommash was the perfect Warsong, an orc who simply loved war and warfare and was rarely seen standing back and directing his people when he could be in the front line of any combat swinging his enormous, two-handed axe, Gorehowl, and screaming his people's powerful, ululating war cry -- the very war song that they took their name from. Somewhat slim for an orc, Grom made up for his lack of ponderous orc muscle with sheer ferocity and a dancer's grace. As the war raged on, Grommash led forces into conflict time and again.
If he objected to orc warlocks' aging orc children overnight to make them warriors, there is no sign. If he commented on Gul'dan's replacement of Ner'zhul, it was merely his intolerance of the scheming, magic-addled leadership of the Horde, as Grommash was an orc of pure action. Impetuous and rash, he was quick to seize a moment for good or for ill.
On the eve of the final battle with the draenei, all the orc chieftains were assembled and told that their great benefactor Kil'jaeden had arranged a boon for them. Through consumption of the blood of the enormous pit lord Mannoroth, they would gain power unlike anything they'd ever known before. Mannoroth opened his own veins and poured his seething, fel-cursed blood into a great container, and Gul'dan offered the orcs the chance to partake. In the end, of all orcs, it was Grommash Hellscream who stepped forward and drank. Seeing the howling fury and power Grom felt after taking the blood, the rest of the Horde (with the exception of Durotan, who refused and forbade his clan to drink, and Doomhammer, who offered a subterfuge that he wasn't worthy to drink from the same cup as his master Blackhand) soon followed Grom's lead.
So empowered by Mannoroth's blood, the orcs of the Horde proved absolutely unstoppable. Soon, Shattrath and all other draenei cities fell. Driven into hiding, the few remaining draenei were no threat to the orcs, and so a long period of stagnation and looming self-destruction came to them. Even the planet suffered from the dark magics of the warlocks, losing the ability to support life. It seemed that the orcs would die out, destroying each other in pointless conflicts after having enslaved themselves to demons who no longer cared what happened to them at all. (It's possible that Kil'jaeden would have returned his attention to his new orc slaves and used them as soldiers in time, if they didn't simply die out first.)
But then Gul'dan made contact with Medivh and created the Dark Portal. Rather than die out, the orcish Horde would go forth and murder another world like a swarm of locusts. Such was the plan -- or at least, the plan as it was vouchsafed to the orcs by Gul'dan, who secretly had his own plans. None of this really mattered to Grom, however. While his people suffered the same fate as other orcs, his intractability and fury had only grown through exposure to the demon blood. Gul'dan convinced Blackhand that Grom was simply too disruptive an element to bring in the first wave of the invasion.
The first orc to drink demon blood, one of the finest warrior lords of his generation, was forced to watch as the orcs marched through the Dark Portal and into Azeroth.