Gravitational Anomaly event

"Strange and impossible things are leaking into your world!" - Starting the event

"''Your world will be filled with unimaginable chaos! HAHAHAHA!" - Bill Cipher''

The Gravitational Anomaly is an War Mode event. While active, gravity is low, similar to the Space biome. The event has a chance of spawning each day after Mechantera has been defeated or with a Contained Portal. The message "Strange and impossible things are leaking into your world!" will appear when the event starts. It will end once Bill Cipher has been defeated. The sky will turn black and have a large glowing white crack in it. All enemies spawn at that crack.

Enemies:
From the crack in the sky, the following enemies spawn:
 * Eye Bat


 * The Possessed
 * Invisigon
 * Bill Cipher (Boss)
 * Black Mage
 * Levitator

Drops:

 * 0-Gravity Simulator - An accessory that weakens gravity for your player. Increases flight time by 10 seconds. Levitator Drop 11.11%
 * Flying Eyeball Staff - Summon item that summons an Eye Bat. Eye Bat Drop 11.11%
 * Contained Portal - Can trigger this event. Any Enemy (Excluding Bill Cipher) 5%
 * Treasure Bag (Bill Cipher) - Treasure Bag. Bill Cipher 100%
 * Chaotic Blade - Sword that shoots projectile that inflicts Nightmare debuff. Black Mage 11.11%
 * Chaos Soul - Crafting Material

Debuffs/Buffs:
Nightmare - Blackout effect, target starts bleeding, take constant damage. Black Mage, Bill Cipher

Notes:

 * After event is completed once, must be manually summoned to redo it.