Daylight serves as a vaccine to the t-Virus in the story. It is used by the player to disable the Virus Gauge, thereby preventing it from completing and ending the level. Multiple Daylights can be collected, which can be passed around and used by other players or AIPCs. A spare Daylight must also be in the player's possession at the end of the level to earn the Remain Hopeful ending, and leaving it with AIPCs - particularly in Yoko's backpack - will trigger the Regretful ending. An additional sample can also be taken for use in an ampule shooter - this will defeat Thanatos-R in the front square in one shot.
Daylight is recovered from a machine in the Laboratory on level 3F of Raccoon University's faculty building. To obtain this, however, the player must first place in P-Base, V-Poison and T-Blood, which are collected around the scenario. The machine stops working, forcing the player to head over to the Second hall to first trigger a cutscene with Dr. Greg Muller.
Birlew, Dan (2004). Resident Evil Outbreak Official Strategy Guide. BradyGames.