One Who Would Lead - Act 4 Side Quest

Start Location: The River Styx
Quest Location: The River Styx
Objective: Free Hipparchus then defeat Charon for his Oar; return it to Hipparchus

One Who Would Lead is a Side Quest which begins by speaking with Antigenes in The River Styx, the fourth town of Act 4. For the first part of this quest you will need to free Hipparchus from his jail cell; you'll find this location almost directly south of the town you picked the quest up in.

In order to free Hipparchus from his cell you'll first need to defeat the Troglodyte Hero guarding him, Orok Skullcracker. With Orok dead you'll be able to interact with Hipparchus' jail cell and free him. After speaking with him your quest will update and you'll need to retrieve Charon's Oar next. You'll find this oar by killing Charon on the unfinished bridge to the southeast of where Hipparchus was found. The bridge's location as well as Hipparchus are shown on my map screenshot below.

Hipparchus freed from his jail cell.

You'll need to defeat Charon for The Road to Hades Story Quest anyway so you won't even be going out of your way to complete this quest. This also means that Charon isn't a push over since he is one of the main bosses you have to fight while progressing through the game.

For the fight with Charon I recommend equipping any gear you have with Vitality Resistance as that'll help you resist the majority of Charon's attacks. Charon will also deal Physical and Cold damage to you throughout the fight, this damage can mostly be avoided though by dodging the geysers and staying away from Charon himself.