Apparently, since you can tell a story about how you joined your element, I decided to do it too.
-----------------------------------------------------------------------------------
A crow cries loudly, and you find yourself stumbling across a grim, barren wasteland. The ground is a dirty brown, and the bleak sky is covered in overbearing clouds. Perched on a post in front of you is the crow of your nightmares, the crow that silences you and invites you into it's gaze. It's eye holds you, and a voice creeps into your head, a sound that sends a numbing cold straight to your core,
"Welcome to my world, mortal."
"Why am I here?"
"Thou hath been chosen."
"Chosen for what?"
"To bring forth darkness to your world; to sow the seeds of chaos, to weave the web of despair, to usher a new era of absolute nothingness."
"Well, that depends. Are you a cute girl?"
"...Mortal, what dost thou sayeth?"
"I'm saying, do you have some sort of physical form that is anthropomorphic and pleasant to the eye?"
"..."
"Is that a yes...? No...?"
"...I shall showeth ye my form, mortal, but beware thou doth not lose yeself to madness."
The crow jumps off if it's perch and lands on the ground, before warping and twisting into a ball of black feathers, and from those feathers emerges a naked young woman with black wings on her back. Black blood is continuously pouring out of her eyes, and where her hands and feet are supposed to be, she has claws instead.
"Feast ye eyes upon my form, mortal, for I fear thou mind shall not be long for this wor-"
I immediately assault her and steal her lips with a kiss. I take out my hard cock and thrust it deep into her vagina.
"Aghh! Mortal! What dost thou think ye be doing?!"
"Well, simply put, I'm going to fuck your brains out."
"Take it out! Take it out right now!"
I manage to put on the sunglasses I keep in my back pocket.
"Not a chance...in hell."
-----------------------------------------------------------------------------------
Meanwhile, in the normal world, someone feels the urge to scream out loud,
"YEAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAH!"
-----------------------------------------------------------------------------------
"It hurts! Take it out, ye filthy mortal!"
I start moving my hips away, relentlessly pounding into her pussy. She lifts up an arm and tries to claw my eyes out, but I grab her before she can do so and start playing with her breasts.
"...Your breasts are surprisingly perky."
"Agh! It hurts! And where art thou touching, filthy mortal?!"
Blood starts coming out of her vagina, which lubricates my movements a bit, but I can't help but ask,
"Oh, hey, you were a virgin? Or is that like, related to the blood coming out of your eyes?"
"Yes! Ah! I was a, ah, virgin, you mortal fool!"
"Gee, you must be thousands of years old or something. And you didn't, you know, get laid at all? I mean, it would explain why you're so uppity, but, someone must've loved you, right?"
"I am the embodiment of Death! Ah! I consume all that is living, ah! What use do I hath of, ah, love?! Stop moving so hard! Canst thou be more gentle?!"
I push my penis into her until she's filled all the way, and force my lips onto hers. I use my hands to grope her butt, massaging it. I circle my hips, trying to spread her more, and this earns me a muffed cry. My fingers are moving all along her soft skin, trying to pleasure her.
"Alright, great, you're starting to get wet."
"The only thing I wish for is for ye to get off of me!"
I firmly grab her butt and lift her off my manhood until only the head is still inserted, before thrusting and slamming her back down.
"Ahhn!"
"Your moans are cute."
"Silence, you filthy mortal!"
"I love you."
"W-what..."
"I love you alot."
"What art thou saying...!?"
"I'll say it as many times as you want. I love you."
"How dare ye mock me!"
"I'm not making fun of you. I really do love you."
"How could ye possibly love me?!"
"I'm having sex with you, aren't I?"
"More like rape! Tell me then, mortal, what dost thou love so much about me?!"
"Well, you were the one who chose me, so I chose you. If you're willing to accept me for who I am, then I'll accept you for who you are as well. Right now, I don't even know your name, but it wouldn't matter even if you didn't have a name, I'd still love you. As long as you say you care about me, then I'll care about you too."
"...Thou art a simple fool..."
"I love you, so I want to make you feel good."
"Wait, don'-ahh!"
I make another deep thrust again. I keep making deep thrusts, causing her to moan.
"S-stop, ah, moving like, ahn, that!"
"Does it feel good?"
"N-no! It hurts! Thou art terrible!"
She's probably lying, but I lift her up a little and thrust at where I think her g-spot is. I must've hit it, as she moans louder than before.
"Ahhhhhn!"
"...Does it feel good now?"
"I...I don't know!"
I keep thrusting at that angle, and each time I hit it, she tightens up around me. She was holding onto me before, but now, she collapses onto my shoulders, while crying,
"S-something, ahh, is building, ahn, up!"
I speed up my pace, thrusting my manhood into her, letting the pressure build up. Finally, my dick plunges deep inside her, and releases the first wave of sperm into her womb.
"Ahhhhhhhhhhhhhhhhhhhhhhnnnnnnnnn!!!"
She tightens up hard around my manhood as she orgasms, and I continue to ejaculate deep inside of her. Her claws are digging into my back, while my cum floods her pussy. I finish ejaculating, and a mixture of her juices and my sperm dribble out. I pull out of her and gently lay her on the ground. I can see a coat of sweat covering her body, as well as my sperm oozing out of her opening. I sit down next to her and we both try to catch our breaths and cool down. Then, I lift her up and pull her into my arms. I embrace her, and feel her slowly embrace me as well. I whisper into her ear,
"I love you..."
"...Thou hast a most peculiar way of showing it."
"Do you love me too?"
I close my eyes and hear her wings fan out. I can feel them covering me, as if to protect me, and I hear her reply,
"...Thou art but a mortal fool...I feel now that I might hath chosen the wrong person...but...I, love ye too. Thou hath stolen my heart."
She holds my face and kisses me. I ask her,
"So, what is your name?"
"Darkness."
-----------------------------------------------------------------------------------
And so, that's how I came to join Darkness. Ta-da.