This guide will cover what key you'll need and where to find the chest exactly. Abyssal Alter KeyFinding the Abyssal Alter Key can be tough, especially in this extraction shooter given the number of items there are available. Abyssal Alter Chest LocationCloseThe key does offer some help for what you're looking for, but it isn't particularly descriptive. To find this chest, you'll need to head to the second map, Brandrgarde, and make your way to the Abyssal Alter area in the top left corner of the map. Down in that trench, up against the right side wall, is the chest you're looking for.