An imaginifer was a really special person in ancient Rome. They were a soldier who carried a little statue of the Roman emperor on top of a pole during the military parades. This little statue was called an "imago," which means "image" in Latin.
Now, imagine you're playing with your action figures and you have one that represents the most important person in all of Rome - the emperor! That's kind of what the imaginifer did, except the little statue they carried was way more important.
The imaginifer had a very important job because the Roman emperor was like a king. Everyone respected and looked up to him, so the imaginifer had to make sure the little statue of the emperor was always front and center during the military parade.
People would cheer and wave at the emperor statue, just like when you wave at the people in a parade. It was a really big deal.
So, an imaginifer was a soldier who carried a little statue of the Roman emperor on top of a pole during the military parades. They helped make sure everyone knew who was in charge and celebrated the emperor's power.