This app was mentioned in 3 comments, with an average of 1.33 upvotes
If anyone is curious, I figured it out. It's a game called Evil Defenders. I've actually played through it twice, but it might be time to go for three.
https://play.google.com/store/apps/details?id=ru.crazypanda.EvilDefendersFree
This is the level I was thinking of:
Evil Defenders https://play.google.com/store/apps/details?id=ru.crazypanda.EvilDefendersFree
is great. Its free with 2 kinds of IAP.
You get 4 or five maps for free, and then you can pay (I think) $8 to unlock the rest of them. I did this.
You earn souls each time you play, which you can use to upload ability. They also sell souls, but I have played through the game twice and never purchased any souls. I would say you earn them fast enough that you don't need to buy any, but just barely. They aren't super generous with the rewards, but you they haven't made it a requirement to buy them to proceed.
Try these:
Horde Defense - basically a KR clone down to the art style
Apple Maniacs - bit simplistic but looks good