The HeroQuest to make a Styx River Sword is a variant on the Humakt Gains Death Quest.
The difference is in the enemies encountered and the method of creating the Sword.
During the Guardians of the Underworld, Winding Way, Sword Bridge or Falling Caves Stations the Questor will be attacked by Vivamorti. These will usually be Vampires but may also be Vivamorti Magi or Initiates. These will take the place of one of the other Underworld encounters. They will try to kill the Questors.
At Styx Shore, the Questor must find the Forge used by the first Hero to make Styx Swords. This requires a tracking or Scout Underworld skill. Once there, Humakt must perform a ritual to awaken the spirit of the Hero and ask him to guide in the making of the Styx Sword. Once the sword has been produced, Humakt must threaten to quench it in the Styx, thus making her his first victim, but the Styx will give Humakt a flask of water to be incorporated in the sword. Humakt must give up his other swords to Jeset and must swear to Styx that the next time he crosses her he will remain in her kingdom. (He may be able to Quest to evade this oath, but many Questors do not return to Hell once they have gained a Styx River Sword.)
Instead of meeting Grandfather Mortal, the Questors will meet a powerful Vampire who has come to stop the Styx River Sword being returned. This meeting will always occur at night. If the Questor does not defeat the Vampire then he will be killed and the sword will be taken by the Vivamort cult as a trophy.
As part of the Iron Grip, the Questor must swear never to lose his sword, never to give it away and to attack all vampires on sight.