OK, so you're a Mythic figure. How did you come to be so? Your Path represents your destiny, but your Heritage speaks of your origins. Interestingly, this may not be something that you are aware of even once you've realised that you are Mythic...
This work explores one route to becoming Mythic, that you might have some demonic heritage. It may come in one of a range of ways, not just having a demon somewhere in your family tree. It might be the result of a ritual, or perhaps a cursed item imbued with the taint of the Abyss is affecting you. Whatever, any character whose alignment is neither Good nor Lawful could have a demonic heritage.
Having a demonic heritage opens up a range of new Mythic Abilities that are available to the character any time he becomes eligible to gain an ability from his Mythic Path. The character may choose to take a Path or a Heritage Ability, picking from the appropriate tier.
All that explained, the rest of the work lists the Abilities available. Many are pretty nasty as you might imagine, but at the 6th Tier you can even put temptation in someone's way with a Wicked Wish... all devilishly good fun, what?
Now, you might have eyes on telling rather more noble Mythic tales, but for darker stories - and of course for antagonists in a Mythic game - these could prove quite interesting.