You must join a legion before entering the legion battle. Click the legion icon to go to the interface.
The legion is divided into eastern and western sea area. You can send application to join a legion or create one by yourself.
After joining a legion, you'll be able to attend the daily legion battle. It starts from 20:30 every day. Click the highlighted icon to start.
Legion battle is auto-attack based. The winner will enter the next round until being defeated. Rewards are sent via mail and only the top 16 players are eligible to receive rewards.