The moment the vessel stepped back into his troupe's tent, Grimm knew there was a difference.
No. That was a lie. He'd known before the knight had entered the tent that something was different. But now, oh now, he could feel it first hand.
Fear and exhilaration shuddered through his frame. He was glad that his small friend, the vessel, had returned unscathed and was approaching to finish the ritual, their child in tow. The Knight was hesitantly looking around the tent for Brumm, whom usually greeted him. Brumm, reliable Brumm, whose traitorous thoughts had been felt, and whom would soon be dismissed from the troupe. The Nightmare Heart was covetous. It held tightly to whatever beings strayed too close, took and held and never let go of the many souls that served the troupe. Not unless it had to. And yet, with bittersweet understanding, in self defense, Brumm would have to be freed from its grasp. It was a tragedy to be sure. In any other circumstance, Grimm would be spending much more time in mourning. But now, oh now, he was in far too much awe to ponder long about Brumm. The troupe leader could sense the small yet deceptively powerful being approach, its empty eyes having finally realized that the back of the tent was now open for it. Awaiting it.
Grimm's heart beat loudly. Or was it the Nightmare Heart? It didn't matter, since both were the same. Wrapped in his wings and perched upon the ceiling, Grimm eagerly awaited The Knight. His spawn followed faithfully behind the vessel, that thing so foolishly discarded by the Pale King. More like the Pale Idiot, Grimm thought giddily. Oh, what a fool! If only he'd known what his masterfully crafted offal would grow to be! He'd seen it through the eyes of his child. He'd watched, peered unashamedly, into the memories of The Knight not too long ago. The Dreams it had recalled itself into by slashing at its own egg with the Dream Nail.
What a horrid, sordid, fascinating sight that had been!
As was the nature of a great heart, all of Grimm's followers, all the spawn of himself and the Nightmare heart, were raised and held with a vicious love. Cared for and kept zealously. To have seen so many young creatures, so many hollow shells, crash and shatter mere moments after birth? To see so many children, with so much potential, so thoughtlessly cast aside? How awful. How wonderful. A spectacle to behold! Grimm had watched the memory of the vessel's ascent with rapt fascination, unknown by the vessel itself. He had watched it cast aside at the pivotal moment by the Pale Wyrm, cast down into the dark depths of its birthplace without its father having ever acknowledged its existence. Grimm had seen it fall to where it never should have risen again, sealed away in darkness forevermore.
And yet? He had watched, nay, felt, when another heart began to beat. As was the nature of a greater being, the Nightmare Heart easily recognized another of its kind when one was born anew in the Abyss.
The wielder of the Void Heart was approaching. Slowly trotting down the hallway towards him. Grimm's core beat faster, the thumping sound it made getting louder and louder. He couldn't wait to see it. Grimm felt a desirous fear towards them. Such a terrible power they held!
Did it know? Did The Knight know what it had unwittingly done?
Before its ascension, it had called to him through the lantern. Before it became a fetal god, it had made a deal with Grimm, with the Nightmare heart. To light the lantern was to call and serve in Grimm's troupe. To dance and die and live forever within the red flame in dream. Did it know that The Heart already held a piece of its empty soul? Did it know that by raising the Grimmchild, it would impart a shadow of its essence forever onto Grimm's form? Did it know how deeply it had bound them together? Or had it, young, lonely, desperate, or simply unaware, had it made its compact with them without knowing the full consequences? Perhaps. Even the White Lady hadn't seen fit to warn it properly, given that she only viewed it as a tool and nothing more. Another Pale Fool, really. To have so quickly dismissed its true potential, even as she realized that it had been consumed in the scarlet ritual, was folly of the greatest degree. Small wonder Hallownest had fallen.
The Knight stood before them now. They paused but a moment, as if listening to the beating heart, then struck with the Dream Nail.
It arrived, invited, welcomed, into the core of the Nightmare Realm. Slowly it approached, cautiously glancing about for danger. For every step The Knight took towards him, Grimm's heart beat ever faster. It was the twilight of Grimm's current life. His newest end was rapidly approaching, yet he couldn't have been happier. Grimm was prepared for their dance. The end of the Ritual was in sight. The Nightmare Heart, ancient and powerful, beat stronger, heavier, filled as it was with anticipation.
Another heart beat in the Nightmare Realm. It should have been a trespass. But nay, it was greeted warmly. Fire and Shadow always moved so hypnotically together, after all. Flame would ever serenade the darkness with dance. As The Knight stopped in the grand chamber and looked up at the center of the realm, Grimm readied himself. He felt more energetic than ever. He would give it his absolute all, as he'd never done before. The Nightmare Heart beat with an unmatched eagerness. Yet underneath it, Grimm heard that other heart beat as well. So soft, so quiet, so timid that even its owner perhaps could not hear it. Beating so gently that perhaps it did not beat at all. But the Void Heart was heard all the same by Grimm. That newborn god, so recently ascended. Grimm coveted it. He would see that new heart's true magnificence firsthand, no matter what it took.
In a burst of flame, Grimm began their dance.