Ring the mariner's bell on the docks that would normally take you outside Freeport and choose to enter the Kunark Expedition. You will arrive aboard the Bane of Prexus.
Speak with Captain Pegg Bristol to trigger the attacking ship. Iksar sailors will bring their ship along side the Bane of Prexus and board the ship. You cannot board the attacking ship. The attacking sailors will board the Bane and will begin killing crew members but remain unattackable to you. Once the sailors become attackable, they will attempt to kill you.
I helped to defend the Bane of Prexus from the Iksar and discovered a chart that gives clues as to how to reach Kunark. The Bane was too battered to continue but the information was brought back to the Buccaneers for study.