Board Thread:Questions and Answers/@comment-67.176.129.52-20150301071508/@comment-26145626-20150301181435

To get to lvl 10 with a unit a lvl 1 or higher of the same unit must be used to evolve it to the next rank. Eventually you will need to evolve arank 2 lvl 20ish unit with another rank two unit which is amininum of lvl 10