At level 40 you will receive the purple curiosity quest from Uri Frostlich asking you which side you wish to join.

Twice a week, the portal to the battlegrounds will be opened. Gather points by slaying other players from the opposing faction along with decimating monsters and bosses. Make sure to gather resources which also grants you points. When players reach 50, 100, and 200 points, they will receive rewards for their effort:

Objective Points
Boss 10
Elite Monsters 3
Monsters 1
Players 1
Gathering Rescources 5