Hi guys. Here's a map of where the chest is after you beat the warpriest and the location of the plates you need to stand on. Plate 1 in the image is behind a door so you need to use your ghost to find the opening above it to get in. The order in which you stand on the plates is different everytime so take it in turns to stand on your plate first. If your controller vibrates then the correct one was stepped on. If your controller vibrates but you hear a clanking sound, the wrong one was stepped on and you need to start again. The order doesn't reset so if you got the first 2 correct and f'd up the third then stand in the same order you did previously. Good luck out there guardians.