Talk to Simon in the counter to accept Arena Tasks. Before starting the battle, you can review your deck first. Once ready, begin the battle. You can attempt as many times as you want but since most criteria will depend on how fast you can complete the tasks or less damage dealt to you, it will be hard to get three stars immediately upon your first visit. Complete all the tasks first for now to get their first-time reward and at least their 1-star rewards. You can always try later when Arnice's level has been increased, with more powerful servans, better gear, and skills.
The videos for the preliminary tasks below are meant to serve as demos and not to show how to get the best rating.
Explore the Arena
Defeat all enemies within the time limit
First Time Reward: 300L
1-Star: 1 / 300L
2-Star: 2000/ Blood Spear
3-Star: 2500/ 1500L
The faster you kill the enemies, the better. It's also better to ignore the chests.
The Power of Servans
Defeat enemies using only Servans. Default Servans will be provided.
First Time Reward: Ancient Dragon Bone
1-Star: 1 / 150
2-Star: 1500/ 450
3-Star: 2000/ 750
Summon all your servans and order them to go on a Rampage. If you can use support skills, the better.
Massacre
Enemies will appear in intense waves. Defeat 100 of them.
First Time Reward: 300L
1-Star: 1 / 300L
2-Star: 3500/ 900
3-Star: 5000/ 1500L
This is a very straightforward task; just go all out and kill. The faster you kill the enemies and the longer you sustain the chain, the better.
Flee For 1 Minute
For a fixed time, run away from enemies without being defeated. Default Servans will be provided.
First Time Reward: 30 Blood
1-Star: 1 / 90 Blood
2-Star: 1400/ 150 Blood
3-Star: 1800/ Mark of Agility
You have to summon your golem and activate its burst to get the aggro. Next, summon the Bisque to trigger its summon skill that will generate a barrier that will protect you from projectiles. Once that's worn out, summon the second golem and second bisque while attacking to build your chain. The enemies can't be killed and the score will depend on how much damage you've avoided in addition to being on the offensive.
Drink Blood
Defeat enemies then issue the Drink Blood command to your servans twice.
First Time Reward: 60 Blood
1-Star: 1 / 60 Blood
2-Star: 1500/ 180 Blood
3-Star: 1900/ 300 Blood
The timer for this task is very short so you have to summon your demons immediately, then issue the command as soon as you kill the very first fiend. Killing the second fiend shouldn't be that hard so you should be able to activate the Drink Blood command almost immediately.
Utilize Special Attacks
Enemies immune to regular attacks will appear. Find a way to defeat them. Default Servans will be provided.
First Time Reward: 150L
1-Star: 1 / 450L
2-Star: 3500/ 750
3-Star: 5000/ Mark of Skillfulness
You'll only be able to summon two servans here. Summon your offensive servan and order them to go on a rampage. Your servants will use special attacks that will deal with the enemies rather quickly. Activate the servan burst if necessary.
How to Transform
Defeat enemies and accumulate enough power to transform. Default Servans will be provided.
First Time Reward: 30 Blood
1-Star: 1 / 90 Blood
2-Star: 3500/ Rusty Cutlass
3-Star: 4250/ 300 Blood
Using consecutive attacks is the best and fastest way to build your devil gauge. Keep building your chain and combos and you'll be able to get the gauge full in no time.
Power vs Power
You must defeat a powerful boss. Powerful Servans will be prepared for you as well.
First Time Reward: Mark of Maturation
1-Star: 1 / 30 Blood
2-Star: 1500/ 90 Blood
3-Star: 2400/ 150 Blood
You can summon a powerful demon here but you also need to deal with another powerful demon. Use your demons' to overpower the boss and defeat it as fast as you can.