For Newcomers who don’t know how to do the quest, or for people who just want to get the exotic and throw the game away again, let me give a TL:DR.

From what we know, the Weapon will first drop as “Husk of the Pit”. A common weapon which is the exotic, but pale and powerless. In Destiny 1, you would have to kill a specific hive enemy, like Thrall, Acolytes, etc. after completing that weapon upgrade, the weapon would then transform into the next stage.

After completing the upgrade requirements for Husk of the pit, the gun can be upgraded to “Eidolon Ally”. Now donning the signature coloring, but still seems empty. In Destiny 1, you would have to fully upgrade (Masterwork, for Newbies.) the gun, and then complete Crota’s End on 400* Light Level (in this case, possibly Master, but that is not confirmed yet.), in which you would obtain “The Crux of Crota”, the last thing needed for the quest.

And finally, after visiting Eris Morn in the Tower, with the Fully completed Eidolon in hand, you could transform the crux into the “Essence of the Oversoul”, and ultimately, transform Eidolon into our reprised Necrochasm.

Now, take some info here with salt, features like the upgrade system for weapons were replaced with the masterwork system a long time ago, along other things, although Husk, Eidolon, and Necrochasm are confirmed to be returning, we do not know what tomorrow holds.

All we can do is delve feet first into hell(mouth)

See you down below!