I just got my 1st copy of the M3, already had my 1st copy of Arty-chan, they are both VERY Strong tanks and well worth the effort to get, fed them each one of my old 4*s that I was using and they are now lvl 24-25... at this level they are useful to me at the highest level missions. Arty-chans special can nuke most bosses or strong points on the missions while Satan is a great rusher along with the Cromwell I have been using for that role... not to mention Atry-chan is only a 4 cost while Satan is a 2 cost!