Umin has become extremely powerful through the influence of his necklace. You must defeat him if you would have any hope of surviving.
How to defeat Umin
One player becomes the "Tank", to keep Umin over the spike traps (note: do not stand on the spike traps, they will damage and kill the players when set off), the tank should keep themselves, up against the south end of the ship, just behind the spike trap there, with their back against the wall therefore avoiding knockbacks and also placing Umin on the spike trap, the second player your "Healer", a Minstrel/Rune-keeper/Lore-master, will begin to chain heal your tank for the entire battle with Umin, the third player the "Trap-trigger" attacks Umin but never gets or keeps agro. At some point Umin will hit half morale, then you start the Part 2.
At this point, Umin's attacks have opened both the south and north ends of the ship, Umin uses the necklace, and becomes immune to all attacks, however there is a way to bypass this shield effect. When Umin strikes at the tank to smash him, he will get his hands stuck into the ship, at this point the trap-trigger will run the south end, on the overhead of where the tank is fighting Umin and step-on the pressure plate, this will set off the spike traps and remove Umin's shield from the necklace, now the tank and trap-trigger attack Umin for as much damage as possible before his shield comes back up. Once the shield is back up wait for Umin to get his hands stuck again, and repeat the spike trap on him.
Eventually Umin will hit less then 100 morale, he will then run to the middle of the ship, to heal himself, do not let him, use ranged attacks and keep hitting him (note: Umin if left alone, he will heal himself back to 1/4 of his morale, when he runs to the center of the ship, if this happens it will set you back to Part 2) but no not chase him to the center, the trap-trigger should now head to the north end of the ship, and step-on the pressure plate there, it will set off the blades trap, and then Umin's fight is over, he is defeated, he returns to normal, and he will now speak with you.