Big Varder is a boss in PSO2. You can find it in the following missions:
- Underground Shafts Exploration
The battle involves going to multiple points on its body to destroy the various cannons and weak points. After you deal with all of them on the bottom, you can climb up the platforms in the front to its upper section where you can fight a large mech. Defeating it will reveal more platforms leading to its central core. Dealing enough damage to it will destroy the boss and earn your trophy.