Review on 🎃 Spooky Sleek: MaleDen Invisible Upgraded Message Halloween - Unleash Your Mysterious Side! by Jonathan Germain

I actually bought these to create hidden areas on Dungeons & Dragons maps. Not exactly what they were intended for, but after creating the cards and then using them in game after about three to four weeks, the ink still appeared under the light. I find this to be a one of a kind item that can be used for many creative purposes and is very affordable. Highly recommended.