What is the Charons favor?

[The Good Guy]

I gave Charon a bottle of ambrosia after buying 10000 worth of wares. Does he do anything after the bond is achieved?

[C4RNIVOR3]

Characters bonds are largely just for narrative. If you're looking for any gameplay rewards for maxing bond, there are none outside of the 6 characters that give a summon item once their affinity is high enough. Charon is not one of them.

[Specific Beef]

But there is a bit in the notes about the eventual v1.0 that promises "new story content for every character!" The "every" makes me think these bits might be connected to your relationship levels with each person. So the benefits of these friendships might be yet to fully flourish.

In the meantime, they're just nice targets that make you chase a certain tactic or trial, and they tend to help you to understand the game or just generally improve. I might not have been doing maxed Extreme Measures runs if it wasn't for Poseidon getting sick pleasure out of it.