Nectar is a drug used by Mantel Global Industries to perfect their soldiers reflexes and danger perception. The problem with the drug is that it makes the soldiers unable to see what they are doing and suppresses emotions, and when overdosed the effect is very dangerous, causing the soldier to not know the difference between friend or foe and making them extremely vulnerable to being attacked by enemies.
When the soldiers do not get their regular dose of Nectar, they experience withdrawal symptoms like hallucinations, loss of color/vision, blackouts & instability of movement. Subjects who do not recieve their required dosage of Nectar are classed as code Haze, meaning they will be experiencing withdrawal, and hunted down by Mantel.
The only known Mantel soldier who has survived withdrawal from Nectar is Shane Carpenter. This is due to the fact that he was involved in a dropship crash, and in the crash his Nectar distributor was damaged, making it unusable, so throughout this stage of the game Shane experiences hallucinations from withdrawal.