培养（Cultivation） is one of the sixteen Shards of Adonalsium. It is unknown who holds the Shard, but Cultivation is female. She is located on Roshar, and originally came to that planet with Honor, before Odium arrived there. She is still alive, and was romantically involved with Honor.
In Words of Radiance, mankind is referred to by some spren as 'sons of Honor'. This could suggest that Spren are not part of Honor.
It has been theorized that Cultivation is the reason why Shinovar is so strange compared to the rest of Roshar.
With the lack of information on Cultivation, speculation runs rampant of what her influence may be. With Honor dead and Splintered, as well as Odium's influence in the Voidbringers, it is possible Cultivation or one of her servants is the Nightwatcher, and that she is responsible for the Old Magic. As the Nightwatcher is referred to as both male and female, its gender cannot be used to prove a connection to Cultivation.
Further support for this connection is found in Interlude 9 of Words of Radiance Lift. Windle specifically refers to her going to the old magic and receiving his mother's blessing. In chapter 3 of Words of Radiance, the dichotomy of spren is discussed. Honor is connected to spren of emotion. Cultivation is connected to spren that represent forces. The conclusion can be made that the Night Mother is the Cognitive Realm manifestation of Cultivation.
It was speculated that Reya, who was said to have shed a single tear and had a star named after it, may be the name of Cultivation's holder, however Brandon and Peter confirm that she is important for a different reason.