To prepare for a difficult combat, you can invite other users to your Party. You can invite other Users through the menu that appears when you click on the character with the mouse.
The invitation completes upon the acceptance from the opponent.

Once the party is made, each others stats and current location will be indicated on the screen.
Also, the members will receive a certain amount of Party exp. points as a bonus.
Maximum of 7 players can join a Party including yourself.

Party related chat Message

/party invite [character's name] : Invite the user to join the Party
/party ban [character's name] : Ban the user from the Party
/party withdraw [character's name] : Withdraw from the Party
/Squad invite [character's name] : Invite other squad leader to join the squad