The sky’s not the limit.

You may be the ultimate god of your world, but sometimes it’s best for that god to design other gods for their world’s inhabitants to worship.

Consider the style of pantheon that would best suit your world, whether emulating an existing selection of deities (for example the frequently referenced ancient Greek, Egyptian, or Norse gods) or designing an entirely new one. Will there be global, racial or regional worship of deities, and if regional, are they different gods or variations of the same?

Decide on the level of religions’ recognition of each other, from familial bonds between deities in a polytheistic pantheon to the denial of all other false gods. Another consideration is the expected level of interaction between the divine and the mortal, from mysterious, inscrutable, barely personified beings to direct divine intervention by avatars. (Though the latter should usually be avoided, as direct intervention by one deity is likely to lead to similar action by diametrically opposing powers.)

Consider the size of pantheon that will work best, whether favoring the broad choice and mystery of a larger pantheon, or the familiarity and accessibility of a smaller one, with fewer temples to compete with each other. A larger choice will better suit an epic, global campaign while a simpler array might be more appropriate for a short, localized campaign. Most popular and classical settings tend to have pantheons averaging approximately twenty major deities.

There are balance and game structure considerations, including adequate representation of all alignments, core themes, domains and subdomains, availability of appropriate choices for all core character classes (not just divine spellcasters) and care with balancing any unique strictures or granted powers.

Consider the reasoning behind the various deities’ ethos and alignment. For examples, a wind god and a rat god may be diametrically opposed, one tending to represent fresh open air, while the other might represent dark, dank burrows and the undercity. But many perspectives can be applied. With a mix of the typical and atypical, you can create a structure that players can relate to while still bringing unique flavor to your world.
Is the rat god chaotic evil, with themes of swarm, darkness, and pestilence, or a lawful good icon for community, coziness and burrows? Perhaps the rat god is a chaotic good deity protecting the underdogs, outcasts, and survivors, or lastly, a lawful evil representative of planned ambush assassins, and the strong preying on the weak.

Similarly, the wind god might be a lawful good deity of messengers, travel and communication (leading to understanding and acceptance, while ignorance leads to chaos and distrust) or a chaotic evil power of unpredictability, insincerity, and violent mood swings. A chaotic good god of freedom, travel, and the wild, or a lawful evil being of might, speed, and dominance, bringing all beneath one supreme ruler, with a strict hierarchy of power and global reach for missionaries; none can escape the Word!

Design of each deity should include the basics, such as ethos specifics and strictures, holy symbol, favored weapon, and vestment colors. Building up from this, you can also add as much detail and complexity as you like, including style of worship (private and/or public, hymns, prayers, scripture, dance, sacrificial rites), temple architecture, relics, holy sites and pilgrimage, prophecies, holy days in the calendar, creation myths, and similar mysteries. You may need to record regional church relations with rulers, laws and the populace (charting the levels of power of the church, from the recognition and respect of a mighty theocracy to the intrigues of a forbidden secret cult). Clergy hierarchy and a further hierarchy toward the divine may prove important, such as saints, angelic or demonic planar messengers, avatars, and finally, the actual domiciles of the divinities in worlds far beyond the mortal realm.