There are a lot of resources to collect in Immortals Fenyx Rising, some of them being easier to get than others. The Charon Coins are very important but can involve some work to get. They are used to upgrade your skills and Godly Powers, making them very important.
To get them, you will need to complete Myth Challenges. These are challenges that you can find in different locations, all over the map, that will test your abilities with one of your mythical abilities. Others might require you to hunt down certain locations, like the Harp Challenges, or to win a simple race.
Finding Myth Challenges is actually quite easy. They will automatically highlight themselves on your map with an icon when you get close enough, and you can also use your farsight ability to find them.
To use farsight, push down on the right thumbstick for a second or two. Then, scan the surrounding area. When your controller starts to vibrate, and you hear a low humming, you will be close to finding something. Scan the nearby area with the reticle, and you will zone in on a hidden secret. Hit the prompted button to reveal them.
They can be anything from chests, or resources, to hidden Myth Challenges. Once they are revealed they will be marked on the map and you can visit them at your leisure. Each completed Myth Challenge will reward a different number of Charon Coins, depending on the difficulty.
To use Charon Coins to upgrade your abilities, you will need to be at the Hall of the Gods. Interact with the vase there to open up the upgrades menu, and you can choose to upgrade skills or Godly Abilities.