Necrochasm

"Eternity is very close. Can you feel yourself slipping?"

- Weapon description

Necrochasm is an exotic auto rifle in Destiny added by The Dark Below. It requires obtaining the Common Auto Rifle Husk of the Pit; upgrading it to the Legendary Auto rifle Eidolon Ally; and upgrading that to Necrochasm with a Crux of Crota rewarded from completing Crota's End on Hard Mode, or with the essence of the Oversoul from completing the 390 Light version of Crota's End.

Like Thorn, Necrochasm is one of the Weapons of Sorrow. It was created from a captured Guardian weapon (likely taken after the Great Disaster) and modified by the Hive to feed on its owner's aggression.

Year 3
In Year 3, the Husk of the Pit can be obtained via killing any Hive Ogre, although the drop is not guaranteed. The weapon is then upgraded to Eidolon Ally through killing a certain amount of a randomly rolled Hive enemy. After the Husk has been upgraded, the player must then kill Omnigul, Will of Crota and then obtain the Essence of the Oversoul from killing Crota in the 390 version of Crota's End. Once those two tasks are complete, the gun can then be upgraded into Necrochasm.

Destiny 2
In Destiny 2 the way you acquire this gun is different. If you completed the Croats End raid on contest mode within 48 hours of the raid being released, you could walk up to the raid vendor at the end of the raid and obtain the quest, upon which you would automatically obtain the weapon as well as the Husk of the pit, Eidolon Ally, and the quest for its catalyst. If you did not, then you would simply obtain the Husk of the Pit and the quest after talking to the raid vendor and must complete it.

The first step is to kill 100 Hive anywhere with the Husk of the Pit, with bonus progress being granted in the raid itself. Once completed, you will receive the Eidolon Ally and the next step of the quest, which requires you to obtain 20 Essence of the Oversoul, which are obtained randomly by completing encounters, however they have a low drop rate. You can also complete specific triumphs to obtains some more essence, though they wont grant you all the essence you need. Once you’ve completed that step, you will be awarded with Necrochasm.

Catalyst
The catalyst for Necrochasm requires you to obtain 35 Essence of the Oversoul, but worry not, as the quest to obtain the catalyst is retroactive as long as you already collected the 20 essence required for the gun itself, meaning you really only need another 15. The catalyst grants the Outlaw perk, meaning faster reloads on precisions kills.

D1 Gameplay
Necrochasm's signature ability is "Cursebringer", which allow the player's kills with the weapon to trigger Cursed Thrall-esque explosions.

D2 Gameplay
In Destiny 2, the original perk remains the same albeit with a noticeable change; the cursed thrall explosions now refill your magazine, and the intrinsic perk, desperation, will grant better stability and aim assist, as well as increased fire rate.

Lore (D2)
Arise for Crota, Son of Oryx, the Hope-Eater!

He who has seized the Sky lair above Ceres, which peers into other planes, now vassal to the might of the Worldbreaker!

Within these keyholes our brood communes with unheard voices. They who whisper that the curse of our Thralls is a blessing granted by the Deep.

Now, in honor of the God-Knight, we fashion these gluttonous whispers into death. His Hellmouth becomes home to the profane: the corpse of the Sky, reborn in the abyss.

— Enkaar, the Anointed

Trivia

 * Necrochasm is the only weapon in Destiny that is acquired by upgrading it from common (Husk of the Pit) to legendary (Eidolon Ally) to exotic (Necrochasm) status.
 * The weapon was referenced in the credits of The Simpsons episode Treehouse of Horror XXVI.
 * In Year 3, Necrochasm is the only Exotic weapon in Destiny other than the Zhalo Supercell that has an elemental burn and requires a player to complete a part of a raid.

List of appearances

 * Destiny: The Dark Below
 * Destiny 2: Season of the Witch