So you are joining a cosplay group and would like to build your own shiny wearables? Adafruit has shared a guide that shows you how to build a Glowing Viking Rune WayFinder. You are going to need a Pro Trinket, Neopixels, battery charger, 150mAh battery, 3D printer, and a few other parts to complete this project.
Adafruit has shared the instructions for this project here.