I bought Panthera when I saw it here because the listing didnt show any IAP and I do like to support premium games. However, they do have an IAP store with a special currency and power ups.
Maybe it was added after you bought it, but both the iOS and Android store currently includes this in the description:
"- IAPs can be used to progress more quickly and more easily through Panthera Frontier, but we recommend playing through using your own skill and ability first!"
It's an interesting looking game, though not many reviews at the moment. I have enough to play at the moment, but I'll be keeping an eye on it.