Extra-long 'Epic' quests are marked with a lightning bolt, and reward 10 stars. For those quests, it's easiest of find a mission in the single-player campaign and repeat it to complete the quest. Many of the quests require you to play as a certain character or use a certain ability, but some target a specific boss character.
Most faction quests can be completed across any game mode, so if you know you'll be spending some time on the Plants or Zombies side, load up with quests from that faction to finish several at once. Quests are split into Plants, Zombies, and Multiplayer. You can earn Stars by accepting Quests on the Quest Board. This guide will explain some of the best ways to earn currency so you can unlock characters fast. Plants vs Zombies: Garden Warfare 2 has a ton of characters to unlock (see our Full Character Guide), but to get them all you'll need money, and lots of it.
