Run directly through the sleeping giants and go up the stairs and enter the room at the end. Run outside from the Pontiff Sulyvahn bonfire, then go left up the stairs. This covenant is located in Irithyll of the Boreal Valley after the Pontiff Sulyvahn boss fight. Easy 'Covenant: Aldrich Faithful' achievement.
If you see any movement, such as an opening and closing lid, that's your cue to get offensive.
Watch the chest closely for several seconds. However, another trick is to stand nearby, outside of potential striking range. Your best bet is to hack apart any chest you find, so that you can get a head start if it winds up having a life meter. Sometimes, you'll get near one and find that it is actually a dangerous Mimic. Not every treasure chest is as helpful as it seems.
