Lifelight is that power by which Lift is accused of being fueled by a human visitor (suspect Mraize) to Raboniel. He states that her master should ask Cultivation "why she made an Edgedancer who is fueled by Lifelight and not Stormlight."
Navani says to Raboniel, "Three gods. Three types of Light." That to which she is referring are Honor, Odium and Cultivation, and each their connections to Stormlight, Voidlight and Lifelight, respectively.