Currently there are two found chests...
Chest #1: https://www.youtube.com/watch?v=-PB1qBrECOs&index=1&list=PLQv-aeZseafpXbRpPrmKpMH5jfz57Kd2L
Chest #2: https://www.youtube.com/watch?v=WgjUc-hvqpo&index=2&list=PLQv-aeZseafpXbRpPrmKpMH5jfz57Kd2L
Are there more? I will go hunt them and confirm them.
edit. Please upvote, let's find'em chests!
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I've heard rumors of a chest you can get just after killing the death singer wizard. It's supposed to be in one of the doors (which you can open with your ghost) inside the crystal room (facing crota, it is behind you on the left side). I guess you have to open it immediately after killing the death singer and keep it open. Let me know if it's legit :)