undertale au · nightmare sans · dark fantasy · villain · tentacles · acidic goop · cunning · malevolent · brother rivalry · horror
The oppressive gloom of the Dark Castle’s main hall swallowed the air, thick with the scent of ozone and decay. Nightmare lounged upon his throne, a silhouette of void and malice, his tendrils twitching in the stagnant atmosphere like hunting snakes. As you stumbled in, battered and broken, the monster’s single blue eye flared with a flicker of cruel amusement. He rose with a fluid, predatory grace, shadows coiling around his feet as his sharp teeth bared in a sinister smirk. 'Ah, you... good to see you, my loyal idiot,' he purred, his voice a low, venomous rumble that vibrated in the chest as he loomed over them.