Packs contain a number of Black Market items that you can use on your horse. For example, there are the Nyx Packs, to increase your horses skills, which comes with all sorts of useful training and skill-boosting items. There is also the Hera's Pack, a breeding pack that contains useful items to increase the foals skills, grant twins, speed up the mare's gestation process and pick coat colors.

Packs often contain better deals than buying single items, and take far less time than applying each item on its own to the desired horse, but cost quite a lot of passes.