Does anyone know what Epos's feather does?

Tom gets a feather from Epos and adds it to his shield. But the book never says what special powers the feather gives the shield. When we tried to google it, we discovered that other kids are reading different versions. Some beasts are named differently and the special item they get from each beast is sometimes different. Also, what that special item does is slightly different. We are reading the Scholastic version bought in the U.S. Does anyone know what Epos's feather does? Thanks.