Once you join a Corps (and are at least HQ level 6), you can access Counterattack. This is helpful for numerous reasons, one of the biggest is that you can purchase a 24 hour Aegis once per day for 100 Loot. To earn loot you have to perform Counterattack battles. There are 4 different targets for you to attack.
Note the "Up Officer" in the lower-right corner. If you use this officer in your attack you get extra rewards.
First, you should Seek Aid from your fellow corps members. From the Counterattack page, select "Seek Aid" and send out requests to members in your corps. It's smartest to seek aid from those who are online (those members are sorted to the top of the list, and labeled as such), and are higher in level (such that they can send you powerful officers). This sends a message to the selected corps members that you need help. They then have to respond to your request by sending you up to two officers to help you with your attacks.
Your corps members then send officers to you to help you make the attacks - you will know you have new assistance from your corps members by the red dot at the top of the Seek Aid tab.
Once you've received aid from your corps members, choose the officers you want to bring to battle. The criteria are the same as for standard Special Operations battles, with two differences: 1) You can use two officers that have been sent from other corps members, and 2) You would prefer to include what they call the "Up Officer": A featured officer that gives you bonuses (ATK +50%, HP +50%, Stage Rewards +100%) if you use them to attack. You can use your own Up Officer, or use one from an ally.
Next, select one of the four targets and attack it. You want to select the highest level target you can defeat, as the rewards are greater. There are no penalties for losing a battle.
The battles are the same for standard Special Operations, so look to that guide for strategy.
You're not done when you win your first battle - there are 20 stages for you to complete. Each time you win a battle the level of the targets increases, as do the rewards.
Counterattack is one of those situations where having powerful friends really comes in handy. If you are in a powerful corps, and the high level players can lend you a level 120 Wendy and/or Forest Elder, even the lowest level player can clear up to at least level 110 just by using Divine Halberd.
Mysterious Maze
When you've defeated the 20th stage of Counterattack, you get a chance to explore the Mysterious Maze. This was added recently, and serves as an extra challenge to gain extra rewards.
To start the Mysterious Maze, first set your formation (choose your officers - you can only use your own officers, not the ones loaned to you by your corps mates.)
The maze consists of 20 steps, and at each step you are given a choice of 3 paths. You can get:
- A reward (supplies that will be added to your inventory)
- A trap (one of your officers is dealt damage)
- A break (one of your officers heals HP)
Always choose the path that has, in order:
- A store icon - you can be given this option every 5 steps. Selecting this path takes you to a store where you can buy items with your loot at pretty good rates.
- A gift icon - gives you supplies or a break
- A question mark - could be a gift, break, or a battle.
- A target - this always leads to battle, and should be avoided unless you have no options (all 3 are targets).
At early levels the battles are all slaughters - you have essentially no chance to win, which you must do to continue in the maze. If you get a battle as your result, your maze journey probably comes to an end for the day.