Lots of fantasy RPGs have toyed with the idea of "epic levels," where your characters become extremely powerful and face epically dangerous foes — but this concept has been hard to pull off. Until now. Mythic Adventures for the Pathfinder RPG lets your character take on unbelievably huge challenges.
In Dungeons & Dragons, and games derived from it (including Pathfinder), the standard levels top out at 20th. Anything above that would be considered "epic." And you can see how it would be awesome to play an "epic" level, where your characters can get way more powerful and face epically dangerous foes — or just straight up battle against gods.
But there's an inherent problem with just scaling the attack bonuses and armor classes and damage rolls up and up and up. Eventually the numbers become ridiculous. If your attack bonus is +85, whatever you roll on your trusty D20 seems pointless. There are other problems with different classes not scaling properly and other game design stuff that I won't bore you with. It's sufficient to say that RPGs have always had issues with high-level play.
This all explains why Paizo's approach to Mythic Adventures is so interesting. It is not a book of stuff for characters above 20th level. It actually adds a separate tier of "mythic power" to characters, giving them access to seriously impressive abilities that go far beyond another D8 for your damage roll. And characters of any level can become mythic.
Here's how becoming mythic works: at some point in the campaign, the characters will encounter some method of accessing mythic power. They might draw the attention of a god, find a font of power, or acquire a mythic artifact. At this point they will undergo ascension and receive their first mythic tier. Mythic tiers are like experience levels, but it's a separate system that runs alongside your usual XP/level-up mechanic. Instead of gaining experience points, you complete mythic trials. Complete a given number of trials and you can advance to another mythic tier (there are ten mythic tiers altogether).
So for instance you could be a fairly average 5th level fighter, but complete a lot of mythic trials and have six mythic tiers. A 15th level fighter might only have three mythic tiers if he underwent his mythic ascension later in his career. The tiers are totally independent of your regular character level.
Players choose a path when their character ascends, each path corresponding to a very broad fantasy archetype (Archmage, Trickster, Champion, etc). At each tier you gain certain abilities, as well as mythic points which you can spend for powerful effects. For instance, all mythic characters can spend mythic power to roll an extra D6 if they've just rolled a D20 (for an attack, skill check or saving throw) and failed. A character who chooses the Archmage path can select an ability that allows her to automatically identify any spell cast within 100 feet and easily identify all the properties of magic items. At higher mythic tiers, an Archmage can create an illusory double and teleport 30 feet away when she is struck by a melee attack, completely negating the attack. Each path has roughly three dozen of these abilities, and they're all fun and suitably epic, far more interesting than simple stat boosts.
Mythic characters also get access to mythic feats and spells, as well as mythic magic items. The bulk of these are basically buffed up versions of their non-mythic counterparts – this is my one disappointment with this book. I wish some of the feats and spells were more interesting than, "This is a regular spell but 10 percent better!"
What does a mythic character do? Fight mythic monsters, of course. This might be my favorite part of the book, an entire mythic bestiary. It's heavily focused on classic, iconic monsters like vampires, mummies, and dragons (each chromatic dragon gets a mythic version, and in case you're wondering, a mythic elder wyrm red dragon is worth 1.6 million experience points). You'll also find monsters drawn from Greek mythology: mythic minotaurs, medusas, a hydras.
The book makes a point of describing mythic adventures and the types of trials you might face, with a heavy reliance on Joseph Campbell's monomyth/hero's journey. There's plenty of advice on making your mythic adventures really feel like incredible, world-shaking events, not just regular RPG adventures with extra hit points. They even include an adventure with an erupting volcano, long-abandoned island, and – minor spoiler alert – mythic dinosaurs.
Mythic Adventures has a companion volume, the softcover Mythic Realms. This places mythic adventures specifically within Pathfinder's particular campaign world, Golarion, and gives you places where characters can achieve ascension along with a host of mythic bad guys. These range from hideous undead creatures to bizarre alien titans that fell to Golarion in ages past. I'm particularly fond of a jungle region that is overrun by kaiju (and they actually refer to them as kaiju). I can't think of anything more mythic than an adventuring party battling Godzilla.
What's intriguing is that mythic tiers can easily be temporary, so you don't have to devote an entire campaign to this material if you only want to dip your toe in mythic waters. The god takes the power away, the artifact crumbles to dust, and the awe-inspiring power fades from the characters as suddenly as it came. But a few remnants of that power stick around, and the heroes' exploits will live on in epic sagas — even as they return to the simple, boring lives of typical samurai/gunslingers and fighter/witch/druids.