This is a simple achievement. Throughout the levels you'll find small floating cat's heads. These are canopic jars (urns). The jars appear only when someone on your friend list died in the game (thanks to Omen66 for clearing that up).
Pick up five of these, and you unlock the achievement. I'm only in the Tomb of the Timekeeper (first level after you get the first piece of Osiris), so it seems that you don't need that many of these jars.