The material here is from the Wilderlands Players’ Guide, with minor adaptations.

The obvious benefit of the deities is the divine power and abilities they impart on their mortal priests and followers. These powers are not limited to clerics. Because the gods are so present in the Wilderlands, many non-clerics have patron deities and can even become champions. Clerics and non-clerics alike can even try to ask for divine intervention by the deity themselves.

Gaining A Patron: Some deities allow anyone to select them as their patron deity. Other deities require those who would have them as a patron to be devout followers, though not themselves clerics or adepts, providing proper worship and living in a manner generally consistent with the teachings of the deity. Still others ignore those who select them as a patron. Generally, a person may not have more than one patron deity at a time unless the Judge allows otherwise.

Invocation Of A Patron: A person who has a patron deity can invoke the name of that patron deity up to once per week, normally in times of crisis or under other circumstances important to the deity’s goals and domains, and thereby seek to gain the aid of the patron deity. If, in the opinion of the Judge, the person invoking the patron meets the deity’s requirements to obtain a patron and if the action attempted for which the person is requesting aid meets the goals of the deity and falls within the deity’s portfolio of interests, the deity will grant a +1 or -1 divine bonus to the person in that situation, at the discretion of the Judge. On rare instances, in the discretion of the Judge, a deity may grant a bonus of up to +2, though never higher. If the Judge is unsure of whether the deity will aid the person, the Judge may require an ability check at DC 10 based on whatever ability is most relevant to the deity, such as Wisdom for a god of knowledge, Strength for a war god or Charisma for a god of song.

An actual cleric or druid (or other divine class) of a particular deity may make a number of invocations per week equal to his or her Wisdom bonus and does not need to make an ability check. Abusing this invocation ability should be met with the god’s displeasure, either by the deity withholding aid in the future or dispatching a divine messenger or portent to deliver a stern warning to the person.

Invoking a patron deity requires both intent and adherence to a religious observance. The character must recite a prayer or sutra, make sacred gestures, burn incense, etc. as appropriate for the deity’s veneration rites. Most gods accept a certain amount of deviation (or creativity) with such rites. While minor tweaks and embellishments might catch a god’s attention, straying too far from the script runs the risk of the prayer going unheard (and thus, presumably, unanswered).

Some deities provide the benefits of an invocation on an ongoing basis, as long as the proper rites are performed in a space. These rites and benefits are specific to each deity’s cult or cults.

Calling Upon A Patron Deity: Worshipers may also call upon their god for divine intervention. Divine intervention is always at the discretion of the Judge. Some deities are more prone to answer such calls than others. Some respond with divine aid or divine servants. Others respond by physically manifesting their avatar on the material plane. Generally, the chance for a deity to answer a call for intervention is 1% plus 1/2% for each cleric level the caller has. Many things influence this general guideline. Deities cannot manifest outside of their normal area of influence. Calling upon Modron to manifest and aid you in Viridistan will be met with nearly no chance of success, while calling upon her in her own city of Modron will yield greater than average success. Such calls should be reserved for truly catastrophic situations, as most deities feel that the power they provide their priests should be sufficient to meet their needs. In fact, many stern and lawful gods will refuse such requests, though many evil gods will appear even more frequently if it serves their evil goals. Again, divine intervention is always at the discretion of the Judge. It should also be noted that divine aid will not necessarily come in the form requested by the caller, but rather will come in whatever form is desired by the deity in keeping with the principles of the deity. A deity is never required to intervene. Abusing this ability will be met with even greater wrath than abusing the invocation ability.

Calling upon a patron deity for intervention requires some kind of religious rite, particularly one or more proper names of the god. Many gods have specific prayer phrases (often sworn as oaths) that are designed to catch their attention. Reciting such a prayer, even at a whisper, will almost surely prick an ear. Whether the god responds is another issue entirely.

Champions: Some persons offer such service to their patron deity that they are designated as champions of that deity. Whether selected as a favored mortal by a fickle goddess of beauty, rewarded for some exemplary service by a god of law, chosen for their devout lifestyle by a pious god or graced by being an embodiment of the ideals of the deity on earth by a god of good, a champion receives some tangible benefit determined by the Judge. Normally, a champion gains one of the following boons for as long as the person remains a champion: +1 to +3 divine bonus to a relevant attribute of the choice of the deity, an ability normally reserved for clerics of the deity, divine protection equal to a divine bonus from +1 to +3 to the champion’s AC, the ability to use a certain spell once per day (normally less than 5th level), a bonus feat he or she otherwise would not have access to, a greater chance of calling on the deity for divine intervention, or in the most extreme case access to a divine feat or ability. Generally, a deity does not select a champion of less than 8th level. Note that clerics do not normally become champions except in extreme circumstances, as deities feel that the abilities they provide their priests are reward enough. The drawback to being a champion, of course, is that opponents of your patron deity will seek you out to thwart, discredit or kill you even more so than they would an average priest of your deity. A deity must have a divine rank of 6 or higher to have a champion and may have 1 additional champion for each 5 divine ranks above 6 (i.e.: 2 at divine rank 11, 3 at rank 16).

Worshipers: Deities are worshiped by the faithful, which is not limited only to clerics or druids. So long as a leader is charismatic and faithful (sometimes not even faithful), that leader can found a temple or church. It is a mistake to presume that all heads of religions are clerics or druids. Sometimes churches and temples are headed and run by fighters dedicated to a god, or by a powerful wizard who has chosen to honor his vile god or by expert merchants. Religious hierarchies can be political appointments or rewards. It is entirely possible to have a church without a single cleric worshiping a deity. Worshipers need only faith, not a specific class. The religions and temples of the Wilderlands reflect this reality.