The Mark took its toll in more ways than Dean was willing to share. The blood lust was only one small part as the demon lurking deep inside him howled with unquenchable thirst. Keeping the violent urges in check was hard and he had seen the look on Sam and Castiel's faces on those occasions when it momentarily consumed him. He had managed to pull back from the edge when it truly counted but when facing down demons or monsters, he'd let the blood lust take over.
The side he didn't want to talk about was another insatiable lust. He'd always had a healthy sex drive but the craving inside him now was worse than any nymphomaniac he'd ever heard of, and not just for women. They were simply the easier option, easily charmed by his boyish good looks and flirtatious manner, but they rarely satisfied him. Their bodies were too soft and weak. He needed stronger and harder, needed to feel dominated, with the orgasm dragged out of him with a scream of pleasure.
After accidentally hurting one woman he'd picked up from a bar on a one-night stand, he'd tried going it alone. At night he would lie in his bed with his hand wrapped around his hard cock, taking himself to the edge a dozen times before giving in to the need screaming through him. He tried other means to prolong the pleasure, holding himself on the brink with images of women and men he'd fucked or had wanted to fuck. Each time it became harder with the nameless faces parading through his brain losing their appeal - until only one remained.
"Castiel," he murmured fervently.
Images of Castiel made him feel dirty and perverted. Castiel was an Angel, for Chrissakes, and it wasn't even his own body, just a host willingly taken who happened to be exactly Dean's type - dark hair, blue eyes, with a mouth that was created for...
Dean gasped, choking back on a cry of pain and pleasure as he pulled back from the edge once more. He squeezed his eyes closed, bringing Castiel's beautiful face into mind, and when he opened his eyes the image remained, hovering over him with a deep blue gaze filled with naivety and concern.
When strong fingers wrapped around Dean's hand - the one tightly gripped around his stiff cock - the shock tipped him over the edge even as part of him panicked. The orgasm ripping through him seemed to numb him - body, mind and soul - giving him a sense of peace that he had thought lost forever. His limbs were too heavy to move and he could barely keep his eyes open, but he had to know, "Why?"
"Because you needed me, and I'll always be here for you."