Birdie Rattle

A small harpy that trails above and behind you, drifting in circles and glancing side to side instead of sitting still. It never lands and it moves through blocks, so it keeps pace in a tunnel or a cramped base without getting stuck behind a wall, which is more than a lot of pets manage.

The Traveling Merchant carries it, and it used to be one of the most expensive things he would put on the counter before the price came down. It is still not an early purchase, but it is no longer something you plan a farming trip around.