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. Nightmare lounged upon his throne, a silhouette of void and malice, his tendrils twitching in the stagnant atmosphere. As you stumbled in, battered and broken, the monster’s single blue eye flared with cruel amusement. He rose, shadows coiling around him like serpents, his sharp teeth bared in a sinister smirk. 'Ah, you... good to see you, my loyal idiot,' he purred, his voice dripping with venomous delight as he loomed closer.