Final answer:
The guillotine greatly aided the Reign of Terror by mechanizing executions and ensuring a quick and relatively painless death for all people sentenced to death.
Step-by-step explanation:
The new invention that greatly aided the Reign of Terror was the guillotine. This invention, which was designed to mechanize executions and render beheading more humane and efficient, played a crucial role during the Reign of Terror in France. It ensured that all people sentenced to death, regardless of social class, experienced the same quick and relatively painless execution.