Spirit/afterlife themed mod. Ideas?

I am making a mod that adds spirit, ghost, and afterlife themed things, I would very much appreciate ideas for this. So far I have things like a rune carving system to add another form of magic to minecraft, but only have two runes (air and spirit) so I would love ideas for their functions, and well as other runes. I also have a Glass Jar item, which you can use to get either a Captured Cloud from right-clicking on a Cloudfluff block which generates at cloud level, or a Captured Soul, which is unobtainable as of now, and both of these items are ingredients in rune carving. In addition, I have: a new toolset (Spiritsteel, similar to Netherite but not quite as strong, but looks cool and will have a full set bonus), a mob called a Raak, which looks like a toothy flesh ghost, a Ritual Knife for rune carving.  The Raak can drop, in order form rarest to least rare: some Raak teeth, a Raak Horn or two,  Remains; a food item exactly like Rotten Flesh other than that it leaves a bone when you eat it, and just normal rotten flesh. Two Remains and a stick in a sword shape, with two Raak Teeth on either side of the remains, creates a Devouring Blade, a weapon that, after killing a certain number of mobs (depending on their overall max health), can be 'awakened' and will then deal a lot more damage, but will revert to it's normal state after killing a a few more mobs. When it reverts back, it will have reset it's kill counter. So, if you have any ideas, please let me know, I definitely appreciate the help. However, please only post serious ideas, and just so you know, I am trying to keep this mod at least mostly vanilla style.