“ There exists a prestigious academy with a history going back hundreds of years. Graduates are highly skilled and very much sought after for employment. For purely traditional reasons, the academy requires its students to become proficient in a skill or area of knowledge that has no use in the modern world. This could be Ancient Egyptian, an antiquated form of writing such as shorthand, knowledge of building or repairing antique steam engines, programming COBOL, etc. PCs who graduated from this academy must be sure to have this skill in their repertoire.”
“ When you sleep, your soul briefly returns to the place where it was created/goes to when it dies, and seeks nourishment. Everybody's soul is created with a little link (or you could say a greater entity calls it back) to that place so that it can return easily, but upon death, the soul returns via that and annihilates the link as if returns.
Also, as an added thingy, you could say the entity supplying the link, or residue of the links themselves, (whichever) is the source of all arcane power.”