Lizard keys look cool and weird and even a little disturbing, like you wouldn't really want one sitting on your bedside table staring at you all night long while you slept. Unfortunately, at present (March 2016), this item has not yet been implemented.
How to Obtain
Who knows? It would make sense for it to be looted from chests, though.
How to Use
Let's hope this key can be used to open a special locked thing in a desert world, and then when you unlock it, amazing and wonderful reptilian things happen!