Board Thread:General Discussion/@comment-67.70.92.41-20151228204640/@comment-108.160.236.193-20160514173653

Okay... Let me try and lay this out as simple as I can....

 Cinder's plan involved spreading panic covertly. That means that Cinder, Mercury, and Emerald needed to preserve their cover as students at Beacon. If they killed Yang, then their cover would be blown, especially since Yang's friends may care a great deal about Yang and find out the truth. Mercury, on the other hand, has no friends, which means no one will notice if he's missing.

If Cinder, Mercury, and Emeralds'  cover were to be blown too early, then  their plan would be exposed and foiled  before they could get near Cinder's end goal.

This wikia contributor also makes a great point.

71.225.146.39 wrote:

Even if it wasn't already a non-sensical idea, if the plan relied on Mercury winning but he was about to lose then just have Emerald cheat for him with illusions as a safety net.