This one was requested a long while ago and was somewhat done by other people since then. Since I'd doing a lot with other NPCs and NPC careers I figured I'd give it my own try! I guess it could be more story focused, but this is how I define NPCs outside of gool 'ol Grim, so this is what you get!
With this you can use the Reward Store to define your Sim as a Sage. Choose one or all three! Or be the Night Wraith. BUT, you have to be a Spellcaster. This also fixes a glitch in the game that creates a new Night Wraith every time one's summoned. That happened because the Night Wraith trait was included in the blacklisted filters and, par the course, I removed most filtered items.
Do you want your Sim to be the active Sage while at Magic HQ? Well, the Sages spawn before your Sim does so in order to assume that position just dismiss them from the area after you arrive. Teleport any Sim has a "Just go Away" interaction that easily dismisses active Sages leaving you to fill their role.
Additionally this grants your Sim the "premade Spellcaster" trait which stops them from adopting the premade Sage uniform given tot hem by the game while at Magic HQ. ALSO it gives them the magic and spell fixup traits. When added to an active household these traits give them a bunch of spells and potions learned in their spellbook. But ONLY when added to an active household, not when the trait is added. So you won't notice an immediate effect. The NPC Sages all have these traits, so I figured they should be included in the package.
Requires the XML Injector.