For E1,E7 achievement
…and so is fusing n(grade-1) gems into the main gems."
That is a great tip.
I easily completed by shear force of towers and amps. Just play field for achievement, no traits, Looming diff. I used Crit hit(yellow) and Armor Tear(purple) gems(had these skilled up to some extent). Crap load of towers and as gain mana, augment with amps and add even more towers, gets to a point of overkill, but gotta do something, and you just want the achvmnt and 3 skill pts….