Rusted Key Prop

My good friend Danny just launched a new Kickstarter campaign called The Lost Adventures https://www.kickstarter.com/projects/3dprintingdm/the-lost-adventures-all-in-one-3d-printable-adventures?ref=63c2br , wherein you can get some awesome combination adventures, 3d printable models, maps, and more all designed to work together. We came up with the idea to make some cool tabletop props that you can hand to your players as part of the adventures, and this is one of those!

The Rusted Key -- This can be printed as a whole piece which will require some slicer supports, or you can print the split version which doesn't need rafts or supports; just superglue together.

The Rusted Key has specific use in The Lost Adventures Campaign, but you could also use it in your own games. What secrets will it unlock?