You awaken, fully formed, steeped in darkness. You know all of what has transpired, and what will transpire should you let it. You know that you have another self, a weaker, cowardly self. You know you can do what he thinks but never acts upon. The shadows at your fingertips beckon, aching for release. Your weakness wishes he were stronger, in control.
(First thought: Wish granted.)
You make your presence known quite vocally. You sneer, enjoying the look of fear in his (your) family's eyes. You take the Rod that you know to be yours and raise it, slamming the girl and the old man into the wall. None shall interfere with what you have planned, and you have quite a lot planned.
(Second thought: This will be fun.)
Those that think the Shadow Realm is better than death obviously weren't born in it like you were. You delight in your (his) father's screams well into the night as the monsters feast on his soul, and for good measure you run his body through a few times. No need for someone like that around in your grand designs. What good is darkness if forever caged? You shudder at the thought, and make to turn, when—
The protector wakes, catches your eyes, and his eyes alone force you back. You wince in frustration as your weaker side returns, screaming over what he (you) has (have) done. You'll let him think that, you suppose. It would serve him well to develop an ego, you think, even as the cloaked stranger delivers a dire warning. You watch with distaste as the boy and his protector embrace.
(Third thought: Your weak half holds you back.)
It will not do to remain where he can sense you, not after you've just taken your first steps. You need a place to hide, but you have no body of your own, not yet. His body would do nicely, but no—they cannot find you now.
If you're to take your weakness's body, you'll first have to gain a foothold in his mind…
You retreat deeper, from the conscious into subconscious, feeling his memory of you fade the farther you go. Your memory of him sharpens, and you growl at his pathetic features. He could never do what you are about to, of this you are certain.
You stop somewhere among his discarded thoughts, a cesspit of forgotten grudges, jealousy and hatred that was never given time to fester. With your connections to the shadows, and his repressed feelings…
(You examine the darkness around you and laugh. A perfect, blank canvas on which to imprint.)
Electricity dances behind your eyes. Yes, here you are safe, here you are warm, here you are nurtured against all ills. To think that your weaker self loathed the darkness, when it has provided you the safest of havens. Here, among the shadows, you are hidden from all eyes.
(So you'll bide your time.)
A maze forms from the very realm you're in. You run a hand along its walls and are delighted to find yourself vanishing into them, phasing through like a spirit would. Here, your weakness shall never reach you, and his protector shall never erase you. And if they should try…
(You'll grow strong.)
Long, sharp spikes jut from the walls, forming a protective cage. The floor around you cracks, forming tiles, each weighed down with a poisonous miasma. On impulse, you ram a hand into one of the shadowy needles if only to test its sharpness. It pierces through cleanly, and you watch as blood runs down your arm, dripping into the floor to disappear. You lower your body to the ground, breathing deeply to catch the scent of the poison, and cough, doubled over in pain, clutching your chest. You smile.
(You'll thrive.)
Hieroglyphics in a language known more deeply than your own thoughts cover the walls. You read them slowly, one at a time. You'll have plenty of time to savor every last secret, learning things you never knew before and will never share with anyone save those you have complete power over.
(You'll live.)
And your weakness can scheme and plot and fret all he wants. You'll be there to snatch the prize, you'll claim his self as yours, you'll have everything you could ever want in your clutches. For now that shall have to be enough. If nothing else, you can afford to linger for this—this promise of untold darkness blanketing the world.
The thought makes you shiver with anticipation, but the time is not—yet—right.
And so (you wait.)