Was running today when I came across this
http://cloud.steampowered.com/ugc/955014677857767847/CB6974351B241106AC5...
I've seen enemies from the adjoining tier at 'border depths' and in danger rooms, as well as some non-random levels, but it was surprising to see a T3 enemy at T1
T1 Red Rovers and Trojans in Ashen Armory.
Not a huge surprise THIS happened. I've seen T3 red rovers in one of the 6-1 missions.