Sanguinemancy

"There are two versions to every kind of magic, including mine. Just because someone has Fiendish magic, doesn't mean that they've made a deal with one. They could have been born with it, like myself."
I watch as the witch makes her way about the room, hair cascading down her back like a crimson waterfall. She's in a sleeveless shirt and a long, loose skirt, her feet bare. It's an unusual look for the Elf but I suppose it fits the hot, humid summer weather.
"It's still of the Pit. You shouldn't use it." I say, eyeing her as she stops by the window.
"If I don't use it, don't practice with it, I can't control it, master it." She drops her head slightly, hair rippling down around her shoulders. "Without mastery over it, it would master me. If I hadn't trained from youth to use it, it would have taken me and I would be lost."
She looks over at me, her blue eyes filled with a dark sadness. "You don't have to like it. You don't have to like me. All I ask is that you don't take your hatred for what I am and what I do out on my people. I hope you can somehow realize that all I want is for them to be safe from the Maiscear and other threats."
"That's why you brought me here?" I ask, almost laughing. "Look, you're right, I don't like you. I don't trust your magic, I barely trust Casters to begin with but I also believe you when you say that you want what's best for your people. I just wish you'd leave mine alone."
"You know that's not going to happen. My people and yours are allies, have been for eight and a haft thousand years. I don't have memory of a time we didn't call Illary our friend." She moves towards a couch, Dragon-like wings hanging heavily from her back, dragging on the ground. I watch as she fights them so that she can sit comfortably. She growls softly at them, irritated at her lack of control. After several minutes she finally gets her wings in a comfortable position and looks back at me. "You can have a seat."
I find a chair opposite of her. "What about your son? Look what happened last month? What if that happens again? I thought I was going to have to kill him, I don't want to kill a child."
"That's why I'm training him to control his magic so that he can prevent that from happening again."
"There's still a chance he will lose control of his power." She meets my gaze, a dark, serious look there. Her fingers trace the scars on her arm.
"I'm well aware of that. Believe me, it's happened in my family before. We've lost several that way and before you say it remember, we can't just not use it. Without practice, without control, it controls us and destroys the world around us." She glances at the door. "Aurora's on her way here. Try not to hurt her boyfriend."
I look at the ground. "I already did that." I whisper, standing. "Have a good day, your majesty."
She nods her head. "You as well and thank you for being civil."
"It's as you said before, our people are allies whether I like it or not. I need to be polite while in your presence lest I loose my position here."

Effect

Summoning a Fiend, killing an opponent, battle, increasing personal strength, etc...

Side/Secondary Effects

Exhaustion, both physical and mental, anemia, black and/or bloodshot eyes, scars up the arms and hands, body malformations, horns, claws, fangs.
In extreme cases, death or summoning the wrong Fiend, destroying the environment in unintended ways, etc...

Source

Fiends. Hell. The Abyss.

Discovery

The exact discovery by the people of Indarie is unknown. The Maiscear just started appearing in small numbers in the early years of the first age, ebbing and growing as the millennia came and went.
Two famous users are Suiathion, who was once an Eledhrim Caster in service to one of their early queens and who's true name has been lost to history and Bartłomiej Gniewek, who was a knight with the Order of the Eternal Sun and fell hard to temptation. Both are now members of the Elgath Order and have fallen hard, becoming Fiends themselves.

Related Deity/Higher Power

Fiends

Material Components

Blood. Could be the Caster's, could be a 'sacrifice' or, in extremely rare cases, a donor but blood is required. Occasionally, other items will be necessary, usually other internal organs or rare magical items.

Applied Restriction

Practitioners can't set foot on sanctified or holy ground. There are some loopholes in this. Only those who have been given this power or taken an increase in this power from a Fiend are blocked from access to such holy sites. Those who are born with the magic, haft-Fiends and those who's parents are/were Maiscear and inherited their powers, can walk on holy ground though they will find the access to the magic dampened greatly.