Every once in a while, Twilight Sparkle encounters a problem where even her profound intelligence can make little headway. Sometimes, instead of thinking the problem away or negotiating with wise words, she simply needs to kick twice as much ass as usual.

In times like these, she will often temporarily summon a human from our dimension to serve as a mobile weapons platform on her back. The humans she chooses for this purpose are a select few—untroubled by fantastic events, skilled with firearms, steady in the saddle and cool under fire.

They are known as the Riders of the Purple Sage.