@nightkami's name means "night god". And any worthwhile night god should be able to offer an Invitation to a Dark Sleep — https://yugipedia.com/wiki/Invitation_to_a_Dark_Sleep —, presumably one that can't be refused.
Interestingly, in Japanese lore, kami doesn't always refer to a god, but also to any spirit that governs something, so a night kami may not always be so divine. (Hence why no DIVINE Attribute.)
Speaking of night, there are more than a few such cards in Yugioh, such as White Night Queen — https://yugipedia.com/wiki/White_Night_Queen —.
Interestingly, in Japanese lore, kami doesn't always refer to a god, but also to any spirit that governs something, so a night kami may not always be so divine. (Hence why no DIVINE Attribute.)
Speaking of night, there are more than a few such cards in Yugioh, such as White Night Queen — https://yugipedia.com/wiki/White_Night_Queen —.