Deep into the forest, where not even birds or small creeping things of the ground would dare go, was a mighty tower. Made of stones black as a demon's heart, the tower pulsed evil. A sick heartbeat, ever thumping in the souls of those who drew too near to the accursed place. It was that Arthuriel, the Demon's Merchant, had made his home. The necromancer found a wicked peace when he walked among the halls of the fortress, the building as vile as himself.
With the arrival of Arthuriel, the fortress' taint began to spread, withering trees and plants. The air turned poisonousness to breathe and whenever a beast or animal fell, their body would rise as a mindless minion of the fortress, and the necromancer.
"You summoned?" A dog-faced beast with twisted horns asked, stepping forth from a swirling vortex or black and red smoke. A jagged sword was in the demon's clawed hand, but as the hooded and cloaked stood before the towering behemoth, he showed no fear.
"I want a demon heart." The necromancer had learned never to display a need in front of a creature of the lower plains, they always made you pay a hefty price for it.
"Oh?" The demon asked, his mouth twisting into a savage and revolting grin. This particular demon, once great angel of the higher plains, loved nothing more then cutting his own kind to shreds.
"Yes," Arthuriel said simply, then waved a gloved hand in the air. Chains suddenly appeared, marked with holy runes, around the beast's neck and limbs. "Your heart." Faster than he would have preferred, Arthuriel drove his hand into the demon's chest, then pulled a pulsating heart. It was dark and pumping a sticky oil. The demon groaned in pain and anger, but did not move. The holy runes prevented that.
"Ho- how did you, Demon' Merchant, bring light magic of any kind into this cursed place?" He said through many clenched teeth.
The necromancer shrugged. "I made a deal with an angel." He said simply before dismissing the fatally wounded creature back to its home plane. No doubt his brethren would enjoy his wounded state very much.
You betray those who serve you, As you did to me, they shall no doubt do to you. A sinsester voice rang in Arthuriel's mind as he pocket the heart.