HTC One M8 :: Why Phone Saving All Images From Apps To Gallery

I downloaded two game apps (monster squad and i can't remember the other one now) and they were both saving a buttload of images to my gallery. These images were included in the app size or if they're duplicates or what I just don't want to be able to see them and I don't want them being downloaded (if they are) after app installation and using more data and space. In the photos app they were all just sitting there below all the photos I've taken and in the Gallery app they were all divided into one pic per album spanning back to almost a year before I actually owned this phone.

I've gone through settings all morning trying to find something relevant and I uninstalled both apps but the images remained. I had to use my computer to delete them all quickly otherwise it would have taken AGES to tick them all and delete via phone.