Complex sentence: It now includes three adventures per issue, one each for low, medium, and high levels; some issues contain another substamtial article as well, which typically provides further details on the setting of one of the adventures.
Split into simpler sentences: It now includes three modules per issue, one each for low, medium, and high levels, and often another substantial non-module article. In some cases, the latter provides more details on the setting of one of the adventures.