There are heaps of unique items to collect in Mewgenics, from an Anarchist Cookbook or necromantic Kandarian dagger, to a helmet made from a dinosaur skull. Almost all of these items tell you exactly what they do. However, the Fancy Bow is less transparent—all you're told is that it's fancy and that you shouldn't get rid of it.
The problem is, this information comes from Tink, and he's not exactly the most level-headed person. Until you figure out what to do with it, the Fancy Bow will sit there hogging space in your minuscule storage box.
