Talk:Rhino (Warframe)/@comment-47.19.52.2-20131211163127/@comment-112.211.201.120-20131211200009

what keys in particular are you talking about? anyway, those keys are used to get you to void missions. each void mission has 3 different towers = 3 different difficulties.

see: http://warframe.wikia.com/wiki/Orokin_Void to learn more about it.