Board Thread:Questions and Answers/@comment-67.176.129.52-20150301071508/@comment-64.87.9.62-20150310191744

I believe that in order to evolve from level 19 to level 20 for any unit you only need to use for the evolution material the same unit at level 1, but I cannot be 100% sure on this as I haven't gotten a unit to level 19 yet.