Traces of Aliens

It could add traces of Alien, the Spaceships (like structures, having even greater rarity than fossils, and also strange lights that appear in the sky at night, if the stars are attached) buried in the biomes: Desert and Extreme Hills and frozen in Ice Bergs. From the beginning being only vestiges, so as to give a sense of mystery, and who knows someday have a new update giving more prominence to this.