I fucking love phylacteries.
So Jews have this thing where they take some strips of parchment with particular verses from the Torah, put them in little black boxes and strap them to their arm and forehead. This allows them to bear a symbol that their hearts and minds are in dedication to god. I only found out about them a couple of years ago when I was walking through the airport and saw the two Jewiest Jews I had ever seen. A quick Google search for "little boxes Jews wear" led me to the fascinating history of the Tefillin, or phylactery.
I was particularly fond of this because sometime before, completely independently, I had started wearing a pill fob on a belt loop with important lessons that I had learned written on scraps of paper inside. There will always be difficult times and in those times we sometimes forget the most important things about life. So whenever I get upset, I'll open up my little silver box and remind myself. You can see it in just about any picture of me that includes my waistline.
I can't help but feel that these two practices share a philosophical link.
So Liches have this thing where they take their soul and put it into a small item, usually a box or bottle, called phylactery. This allows them to operate their undead bodies remotely. If their bodies are then destroyed, perhaps by a wandering group of adventurers, no damage is done to the spirit and the body can be rebuild in a matter of days. In order to permanently destroy the Lich, you must first destroy its phylactery. However, they are usually guarded by powerful spells, powerful creatures, and hidden deep within keeps or catacombs. It's a pretty ingenious survival plan... well... depending on your definitions of survival.
Either way, phylacteries are about taking something of great spiritual significance, and putting it in a small box. There's something about the idea that I find fascinating.