Capricorn is the Zodiac sign for the goat originating from the constellation of 'Capricornus' which is supposedly shaped like a goat
There were no unicorns on Roman shields. The Roman legions had their emblem on their shield and no legion had the unicorn as an emblem. The closest thing was the carpicorn, which was the emblem of five legions: I Adiutrix(rescuer), the II Adiutrix II, the Augusta (Augustan), the IV Scythica, (Scythian ), and the XXI Rapax (rapacious)
The solution is that Fenoglio writes a new ending to the Original Inkheart story in which the Shadow, which is read out of the new ending by Meggie, destroys Carpicorn and those of his men that had murdered (except Basta). Then when the shadow is finished it disintegrates- releasing all the innocent people who it had killed over the years.