Mittelborg: City of Mages (UP)

Not hard to do just upgrade garrison, tower and hall of fame to max (lvl 3) before tempest 12 which gives you a lot of time.

Gets significantly easier with each life due to the bonusses you get.

Be aware that the whole game is buggy and seems to treat your first 2 Lifes like a Tutorial without the ability to unlock achievements.
If you fulfill this condition during the totorial you need to delete your save, redo the Tutorial and do the condition again