Canterlot Castle's Royal Guards haven't had the best track record when it came to doing their jobs as Canterlot's defenders. This hasn't gone unnoticed by Princess Celestia and Princess Luna.

When the sisters pondered the reason for their guards' ineffectiveness, Luna concluded that Celestia's motherly nature toward her guards – as well as all her ponies – had prevented her from ensuring they received the proper training. Therefore Luna volunteered to personally turn the guards into buff, mean, fighting machines.

That is, if the guards could survive what the Princess of the Night had in store for them.