Octavius the Conqueror

After arriving back to the mainland the party will begin to hear stories of a strong warrior claiming to be Octavius, the champion of Elustria. They will know that since King Krieg has yet to call off the attack on the North Isles, the soldiers sent out to fight the Grave Walkers will be quickly killed by Octavius since he is far more skilled than the common soldier of Ultribar. If the party begins to look towards helping his victims, they will hear that there is a wealthy benefactor who is offering a bounty for Octavius to be taken in alive. If the party wishes to take on the contract, they can go to the Silver Dwarf, a tavern in the city of Ultribar.
After arriving to the tavern they will have to wait until the last call for two figures, an elder and a scrappy looking woman will walk in. One will be Father George, a human in charge of guarding the temple of Ultribar. He will say that he has brought along his student Rosey, an acolyte and ranger who will be able to guide the party on the way to finding Octavius but will not be able to fight Octavius. The Father will offer 500 gp for Octavius to be brought back alive but will still provide 200 gp if he is killed and evidence is brought back. Rosey will not expect a cut of the pay unless she is expected to help fight Octavius as she has the stat block of a Scout.
While on the water, the party will be able to spend the two day trip doing a few different things. The Father will offer scrolls on the island that the party will be going to, if these are read Survival checks will have advantage on finding Octavius. Additionally, the party can hasten the journey by assisting Rosey in manning the ship. This will bring the party a short ways from shore where Rosey will tell the adventurers that they will need to swim to the shore from there and that she will return daily at dusk until they are ready to be retrieved or until they free the port from the control of the Grave Walkers.
After entering the island the party will find themselves in a familiar environment with a dense jungle covering msot of the land. They will hear in the distance the screams of a small ambush inland. If the party succeeds on a DC 15 Survival or Perception check they can make it to the fight before the Ultbarians are dead, if not they will find Grave Walkers looting the corpses as well as dragging them to Elustria's castle. During the fight, the cultists will be wounded and start to make a break for their bandit camp where Octavius will be waiting for an attack on a town on the island, called Vinewall.
If the party attacks the camp directly they will know that they are outnumbered but it will mostly be occupied by undead soldiers and a few mages. The party will have assistance from the group of Ultribar soldiers if they were saved in time. If the party waits for the attack on Vinewall, then it will even the odds more so the party can focus on fighting Octavius. If the party has a passive perception of 12 or higher, they will notice that the mages have began to cast a ritual spell. If five rounds pass before the mages are killed, a group of three ghast will be released onto the battlefield to siege the village. If Octavius is kept alive no one will make an attempt on his life and he can be held on the ship for the night until the battle is over.
After ending the siege, the village will celebrate the party, throwing a festival and treating the party to whatever they can afford to give. They will be treated to a free place to stay but come the morning Rosey will urge the adventurers that they need to report back to Ultribar immediately. Additionally, if they party was not cured of their half-dead condition they will hear now of a monk named Gaia who resides in the desert of power that may be able to help.