You can add a friend as a team member. You will both get 5 Attribute points each. You can also use 2 of your team members' primary card to defeat the Super Villain at the end of each mission.

At level 1, you can have up to five team members. Starting at level 10, your maximum number of team members increases to six. For each even-numbered level following, your maximum number of team members will increase by one.  You can have a maximum of 50 team members at level 100.  Further leveling does not add more team member slots.

If you remove a team member, you lose that 5 attribute points from your energy, attack or defence. Points removed from this function are taken from your highest stat. When you re-add another new team member, you re-obtain the 5 points. Keep in mind, however, that if you remove more than one team member within a 24-hour period, you will be charged an additional attribute point penalty (for a total of 6 points lost) for each subsequent removal, while only being able to gain back 5 when you add a new team member back, resulting in a permanent attribute point loss.