A photograph of the reader’s ceiling accompanied this question. Although we appreciate the photo, it is too far away to see anything but beige dots on a light blue background. We don’t have any idea what creature that looks like a blister and has a sword might reside on a ceiling. Most insects don’t carry swords, but some do have horns that could appear to be swords. However, these are usually caterpillars, and from photo we can definitely rule out caterpillars.

Without more details or a better picture, we are unfortunately unable to make any identification on this creature. We invite any readers to comment with ideas they have about this mystery!