For seven days, Nicolai contends, and then confers, with his new ally.
On the first day, he and the demon contended over his body. He found himself reaching for things he didn't mean to, saying things that he didn't intend, walking paths he'd never meant to before, as if his body would wander off on its own if not properly supervised. It took, Nicolai realized, a special kind of vigilence. A special kind of deliberation required for every movement, so that any unscheduled gesture at all would be immediately recognizable and could be checked. It wasn't very hard. Nicolai had been doing something much the same ever since he was a child.
On the second day, the demon's tests moved to his mind, sounding his defenses. Nicolai had an easier time with this. He had been expecting this type of assault, and though he could feel the demon's power, his own preparations held firm, for the most part. He could feel its influence, its probing touch, in odd flares of anger, hunger, despair, lust. But he knew himself well enough to know those feelings for the anomalies they were, and a few moments' concentration tamped them down until they subsided altogether.
On the third day, the demon went after his soul. Which, as Nicolai had always suspected, was quite apart from the mind or the body. He was less prepared for this, was only warned of it by a slim trickle of darkness that was not his own. A whiff of corruption. A swift clench of evil, not reaching to crush, but to twist, to bend, to mold. Nicolai's instinct was to pray, but the words stuttered on his tongue as the demon laughed. Think you that your God will help you now?
It was true. If Nicolai had ever thought himself worthy of answered prayers, he certainly wouldn't be now. He almost panicked. Almost.
He gritted his teeth. He didn't need holiness. Only purity. Purity of spirit. Purity of purpose. Purity of will, if nothing else.
That day was a long, hard battle. He spent most of it on his knees, praying to no god but himself. But when the moon came up his soul was still recognizably his own, and the demon was disgruntled but vaguely admiring.
On the fourth day, Nicolai rose and washed, ate and dressed, turned his face to the sun and demanded that the demon share its knowledge with him. It laughed. Nicolai breathed in deep of the morning air and attacked.
He caught the demon off-guard, he was sure. The thing lashed in his mind, strong and dark and magnificent but somehow awkward, hemmed in. It wasn't used to being in a human host yet, and its few seconds of adjustment allowed Nicolai the advantage. It was a pointless battle, to be sure. Neither of them would truly hurt the other: they were each too valuable to each other. It was a cockfight. A sparring match. A "men's thing", as his mother would have called it.
The demon lashed out, and Nicolai lashed back with everything that he was. He would have what was his. He had sold himself as sure as any whore for what Astaroth could give him, and he would. Have it.
They grappled as the sun rose and fell, and in the end, the demon's hissing curses turned to surprised laughter. It whirled away in his mind. Very well, human.
On the fifth and sixth days, they conferred. The learning was like nothing Nicolai had ever experienced. Not so much a listening to words as an absorption of raw knowledge. Astaroth answered every question Nicolai had before he could fully form them into coherence: cosmology, arcane secrets, rituals of blood and bone and power so primitive that none but the demons themselves remembered them. Sometimes Nicolai's lines of inquiry edged on mysteries that he could barely comprehend. Astaroth would answer him, though Nicolai felt his mind buckling uncomfortably under the knowledge.
To Nicolai's surprise, the demon demanded reciprocity. Politics, geography, culture, languages...it absorbed them all. The better to serve him, it laughed. Nicolai didn't believe it for a moment, but he figured that it was a fair trade.
It was not quite a truce, not quite an alliance. But it would do.
And on the seventh day, they rested.