“A True Arena Champion” is a side quest in Wuthering Waves where you will compete in an arena after saving an Exile at his request. This quest will reward you with the following:
2 Medium Sealed Tube
4 Medium Resonance Potion
4 Medium Energy Core
6000 Shell Credits
Aside from this, during the conclusion of the quest after talking to Zeyuan and Examiner Exile, you’ll get:
140 Union EXP
4 Basic Resonance Potion
6 Basic Energy Core
6000 Shell Credits
Aside from the rewards mentioned above, you will get a Premium Supply Chest and the “A Desperate Gamble” trophy after completing the quest.
The Premium Supply Chest will have the following rewards:
50 Union EXP
40 Astrites
5 Wood-textured Shards
1 Basic Resonance Potion
1 Medium Sealed Tube
1 Advanced Energy Core
12000 Shell Credits
How to Begin A True Arena Champion Side Quest
To start the A True Arena Champion side quest, you must find an Exile surrounded by Tacet Discords. When you are near the area, you’ll get a quest on the side saying to save the Exile. Once done defeating all the enemies, talk to the Exile, who’ll introduce themselves as Zeyuan, and he’ll talk to you about the Seaside Arena. This will now appear on your Quest tab.
Talk to Zeyuan near an Exile Camp
Go to where Zeyuan is, which is indicated on the map. He will say he will get you an access pass so you can enter in and out of the camp anytime. Next, you’ll inquire about the situation in the camp, so talk to the Exile Leader and Smiling Exile, as indicated by a quest marker.
Talk to the receptionist and apply for the Seaside Arena
Talk to the receptionist. He will tell you that to join the Seaside Arena, you first need to collect three badges indicating you are worthy to enter.
Complete the First Trial
To complete the first trial, you must climb the top of the camp to get the gun. There will be quest markers guiding you to the top. Follow that to reach the top. You’ll see a Standard Supply Chest along the way, so grab it if you haven’t. Grab the sniper rifle and talk to the receptionist. He will give you the first badge, the Badge of Courage.
Complete the Second Trial
The second trial is a shooting challenge. Use a Pistol Resonator, like Chixia and Aalto, to shoot the targets around the area. Once finished, you’ll get the Badge of Speed.
Complete the Third Trial
The third and last trial is a battle against an Examiner Exile. But before you can do this, you’ll need to wait until 5:00 and go to the area marked on the map. Defeat the Examiner Exile to earn your last badge.
To change the time, click on the Terminal 
and look for the Clock icon 
at the bottom of your screen. Click on it and drag the time to the desired time and click confirm.
Defeat the enemies to qualify for the championship round
There will be three rounds of battles you need to defeat first before challenging the Gladiator Champion. This will be a continuous battle, so prepare accordingly.
Talk to the Gladiator Champion
After finishing the three battles, you are now challenging the Gladiator Champion. He will tell you that your fight will commence at noon. But before this, he will contact you to back down from the challenge, but the Examiner Exile will come in, and the battle is set.
Defeat the Gladiator Champion
After setting the time to 12:00, go to the Seaside Arena. The Gladiator Champion will have two phases of fights. For the first phase, you can focus on the Gladiator Champion itself, as it will instantly end once you defeat him. For the second phase, you’ll need to defeat all the enemies.
Bid Farewell to the Arena Champion
After the battle, talk to Zeyuan and Examiner Exile. Lastly, talk to the Gladiator Champion to conclude the quest. You can now claim the Premium Supply Chest and the rewards we mentioned.