KronosNotMe

Do we know what the spren of Night is, we seen Stone and Wind but we get no interactions with Night. We know that the 3 bondsmith spren are related with the ancient spren, but we don't interact with Night or the Nightwatcher directly at all. ( Dalinar, Taravangian, and Lift all interact with Cultivation if I remember correctly) Does Night have any connection to Nightblood or the Night of Sorrows? Is it in another Cosmere book? Where did the Spren "Leave" to, and is that where Cultivation goes?