Support Characters can fight with you in this world only.
Keep in mind, they are considerably weaker than you are.
Their stats are set and will only go up when the community levels up.
When you battle with these, make sure your opponent knows, and if they agree to it, post their stats at the start.
When attacking a support character, you must specify.

Riku:
HP: 30
MP: 2
STR: 1-3
Ability:
Souleater Slash
-2 MP
x2 STR (1 Turn)
+ HP = to Attack (HP goes to main person, not Riku)