"Parallel quests" refers to separate or alternative paths or activities that run alongside each other, often happening simultaneously or independently. Full definition
Players will also be treated to additional customization options, quests, and skills including: new outfits, five new parallel quests, eight new skills, and eight new super souls. (catwithmonocle.com)
I started to enjoy grinding my way through parallel quests for that much needed experience. (nonfictiongaming.com)
You can take a look at all the beta Parallel Quests here. (animegamesonline.com)