When a Nether Reactor is manually deactivated (by removing the core before it appears "used up"), various issues occur:

• Nighttime is eternal, unless one goes to sleep, but even then, daytime only lasts about 20 seconds, then quickly fades to nighttime.
• Hostile mobs no longer spawn, though already spawned hostile mobs remain.
• At times, hostile mobs behave oddly. e.g.: A spider might stay in water, ignoring the player, but will still cause damage if the player comes in contact with it.
• Laws for gravity and liquids flowing are disabled..