Exhaustion and Sleep Deprivation concept: Characters require at least 6 to 8 hours of sleep per 24-hour cycle.Fighting Fatigue: Players can use stimulants, willpower checks (Constitution saving throws), or magic to stay awake past the point of exhaustion.The Consequences (Levels of Exhaustion):Level 1 (18+ hours awake): Disadvantage on Perception checks.Level 2 (24+ hours awake): Speed halved, disadvantage on ability checks.Level 3 (36+ hours awake): Disadvantage on attack rolls and saving throws.Level 4 (48+ hours awake): Hit point maximum reduced, risk of falling unconscious randomly during low-stress moments.Overriding the Void: Pushing past natural limits requires a growing DC Constitution saving throw every few hours, adding stacking debuffs or temporary "Shadow Exhaustion" HP loss