After boarding the LMS Intruder, speak with Slaughtergrott the Vigilant. You must continue through all the quest dialogue, not just accept the quest as soon as it pops up, in order to start the event.
Eventually the a Rallosian Captain will spawn. Kill him to complete the quest.
Note: To exit the boat in The Feerrott you must wait until Slaughtergrott is finished casting. Continue to kill the spawning soldiers until she is done, then speak with her to leave.
Alternatively, if you do not want to wait until Slaughtergrott is finished casting, you can attack her. Killing her will return you to the Thundering Steppes docks. Make sure you have completed the quest before doing this, however.
After the quest is complete, in order to receive your reward, go to the Thundering Steppes and speak to Scholar Milnik on the docks, at ( -550, -16, -430 ) Copy/waypoint -550, -16.45, -430.