Gil McMartin tells you that the Dismal Rage has been increasing their ranks at an alarming rate. You need to crash the initiation ceremony.
Enter the zone "The Dismal Den" in North Freeport. It is behind the Temple of War. Head upstairs and speak with the Qeynosian Scout.
Grab the key from a chest in the far room downstairs. Use the key on the door next to the Qeynosian Scout. Kill the monsters inside of this room to stop the summoning.
Return to Gil McMartin.