You guys are just too smart! The very first guess from Aurora B is correct when she called it "a blob of hot glue". It is in fact an accretion that is formed drop-by-drop when a hot glue gun with a slow leak is left on for several hours. If forms a relatively symmetrical structure, as each drip runs to the lowest point where it hardens. Pictured below are two of them oriented in the way that they are formed.

Aurora B, please send me a convo on Etsy to receive your prize.