Stories have always been told of those mortals bold enough to gain the attention of the gods and become the mightiest of heroes and adversaries. But even among those legendary figures who have earned a deity's favor, tales of becoming one's herald are rare indeed—only the worthiest and most devout mortals may be considered to become a living, breathing aspect of a member of the divine.
Unlike a deity's true heralds—ancient and powerful extraplanar beings who live only to serve—a mortal herald has the free will and basic nature necessary to inspire others to act, for good or for ill, with that deity's will in mind.
If a character somehow manages to gain a deity's attention and proves her worth to said deity, that deity may visit the character—appearing in person or in her dreams, teleporting her to its domain, and so on. The deity may then make her an offer to become a mortal herald. For a non-mythic character, this is a moment of ascension; for one already mythic, this could be at the end of a trial that grants another tier. In either case, the mortal herald is always a mythic being with the same alignment as the deity (though not all mortal creatures that serve a god as holy messengers are mythic beings).
This offer is not made lightly or with subterfuge.
Deities watch carefully before choosing a mortal herald, for investing such power also means creating a new liability if the mortal is not up to the challenges ahead.
The benefits of being a mortal herald vary from deity to deity, and are always personal: a gift of a powerful relic, recognition from worshipers that you are a direct conduit to the deity, access to that deity's godling path ability, and so on. However, there are drawbacks to being a mortal herald as well: the god's ever-watchful eye is on you, as you hold a portion of its presence; foes of that deity also recognize you as a direct conduit; and your soul is undeniably your deity's in the afterlife.
The trials capable of garnering a deity's attention are both harrowing and personal to that deity. Accomplishing such a trial usually puts a character in the good graces of that deity while also earning him the enmity of those who oppose that god or goddess. Not every trial necessarily results in the subject becoming a mortal herald, as the deities show gratitude in a number of cryptic and mysterious ways (if only to encourage a mortal to continue such actions).
Mythic characters who complete a task appropriate to their deity (at the GM's discretion) may take the following universal path ability at 1st tier or higher.
You become a mortal herald of your chosen deity.
Choose a domain granted by your deity. Once chosen, this cannot be changed.
By expending one use of mythic power, you may cast a domain spell granted by that domain as a spell-like ability (caster level equal to your character level), provided the spell's level is not greater than your tier. In addition, if you are at least 6th tier, once per day you may commune with your deity (as the commune spell). If you expend one use of mythic power while doing so, this ability is a free action and time stops (from the point of view of everyone else) to allow you to ask your questions and receive answers instantly.