Some scholars of theology believe that all the world actually only worships a single pantheon of gods; it's just the names and representations of them that differ, as well as regional importance of one god over another. Others resist that notion, calling each nation's pantheon of gods a unique set, specific to that culture, although cults may migrate from culture to culture from time to time.
Be that as it may, these are the gods that have temples in your area, as well as a handful of others that are also worshipped. Although, honestly, people in general are better described as "superstitious" rather than "religious." Offerings and invocations are tossed off out of habit, and people have a healthy respect for the ability of a displeased god to give you a really bad day, but they don't often otherwise pay particular respects to them. Pick whatever domains or favored weapon you think are appropriate if playing a cleric or other class that needs domains.
The way the pantheon works is that no god has "primacy" over another one according to myth. The various gods work in their respective sphere of influence, and their importance varies from region to region. Because the gods appear to be "hands off"; how their worshippers view them, and the popularity of their cults, evolves over time. If the gods exist at all, they may not resemble what mortal worshippers think of them anymore.
While many gods and goddesses have priests or priestesses dedicated solely to their worship, few people worship one god exclusively, including most clergy.
Czernovog (CHERN-uh-voag) "The Black Prince" - As his name implies, Czernovog was originally a Balshatoi god; perhaps even the chief god of that people. His cult has spread throughout the surrounding area, however, and he is an important figure in the religion of the Terrasans, and even moreso in the religion of Baal Hamazi, who view him as their divine "father." In most representations, he looks like an ideal hamazin; jet-black skin, handsome, sharp features, and a crown of six horns poking up through his hair. His concerns seem to be with civilization, although that has taken on a darker pall in many cults, where he's also seen as the patron of the seedier side of civilization: thieves, plague, corrupt politicians, bandits, and worse.
Perun (pare-OON) - He also sports an originally Balshatoi name, but Perun, "The Thunderer" is associated with war, and as such, his mystery cults have suffused the Terrasan military for generations. As he's worshipped today, he's a hybrid of the original cult of Perun and the cult of the war-god of the south, Belcadros, and is sometimes referred to in full as Perun Belcadros. Perun is usually depicted as a primitive warrior, wielding a spear, hammer or ax, all of which are metaphors for his thunder and lightning.
Ashtarte (ash-TAR-tay) - Also known as Ishtar or Ashtar, depending on the dialect of the speaker, Ashtarte is one of the goddesses most associated with civilization. She's sometimes known as "The Divine Librarian" or "The Goddess of Knowledge." Her search for knowledge is only one aspect of her worship, though, and older cults still remember her as a more generic goddess of civilization, to whom fertility and animal and crop husbandry was as important as knowledge. To this day, heirodules, or "temple prostitutes" make up an important part of her religious observances.
While the search for knowledge is an important part of her worship, and the libraries of her temples are amongst the greatest in Terrasa or beyond, Ashtarte's priests are notorious for lusting after knowledge they shouldn't have, and the more forbidden the knowledge, the more they seek after it. Even the old myths talk about Ashtarte stealing forbidden knowledge in scandalous ways (as a courtesan, or through murder.) The temples of Ashtarte have to cover up the scandalous actions of her too-curious priests with disturbing regularity. Ashtarte is usually pictured as a voluptuous naked women with angelic wings, seated on a coiled serpent for a throne, and with a smaller serpent in her hand. In her other hand is a book.
Orcus (OAR-cuss) - The God of Death is not much worshipped or revered locally, but since his temple has charge of preparing dead bodies for funerary rites, it remains important nonetheless. Ironically, the priests of Orcus are notorious for trying to escape death---urban myths of the priest of Orcus who turns to dark necromancy are common bogeymen that mothers use to frighten their children. Orcus himself is never pictured out of superstitious fear; nobody knows what he's supposed to look like---or if they do, they're not saying.
Dagon (DAY-gonn) - One of the most respected and revered gods near any body of water is the Lord of the Sea. Since literally everyone in coastal areas depends on the sea to some degree or another---either for food, livelihood, or at least in the hopes that it won't rise up in a tropical storm and wipe them off the map---Dagon's ceremonies are the most attended of any in those regions, and icons of him appear in almost every single building. He's usually shown as a merman with a flowing beard, but he's also occasionally pictured otherwise; one popular variant is a shark-like creature with grasping tentacles and mouth and eyes similar to that of horrible deep sea hunters.
Veles (VELL-us or VELL-eez) - Veles is the goddess of magic, and few are the arcane spellcasters who don't at least give her some nominal votive offerings from time to time. Her priests are famous for selling charms that protect the faithful from minor harm and bad luck. Most people agree that they do indeed work, although some decry the practice as charlatanism.
In the myths of many peoples, she is linked with Orcus, but the nature of that linkage is obscure, and varies from place to place.
Susinak (SOO-sin-ack) - Susinak is the ultimate traveler. Most people about to embark on a long journey will stop by the temple district and touch the hem of the robe of her statue. Most cities have a brass statue of her in an important plaza, but temples are few. Clerics and other faithful clean and polish the brass statues daily. They do, in fact, frequently start to lose some of their detail and definition because of the constant polishing.
The etymology of Susinak is unclear. While clearly not a native word in Terrasan, she is a goddess who's cult originated in the south, perhaps amongst neighbors of the old Terrasans.
Charun (char-OON) - Charun is a bull-headed god famous for his feats of strength. His temples are small shrines that are simply a roof supported by four pillars with a granite altar in the center.
Selvans (SELL-vans) - "The Horned God" is often seen as a dark god; a representation of nature "red in tooth and claw, and frequently associated with wolves or wulfen. Hunters and outdoorsmen worship him, but these are hard and cynical men, usually. His depiction is common, but his name varies wildly from place to place. He's also known as Cernunnos, Herne, and in the southwest, in Kurushat, as Yinigu. There, he is seen as the patron of the entire nation, and associated with hyenas instead of wolves. It's possible that all of these have different root myths for a similar figure which has merged in the minds of the more cosmopolitan modern world.
Vanth - The God of Penitance is not a popular god, but one that you occasionally hear about from those who have had to spend time in prison. He encourages extremely dilligent penitance and flagellations, so his followers are at least easy to spot. Mythology supposed a link between him and Orcus and Ashtarte, usually hinting that Vanth is a discarded lover of Ashtarte, and a former prisoner of Orcus.
Moloch (MOLE-ock)- The god of fire and the sun. His worship is more prevalent in tropical, open areas (unsurprisingly) where he is seen as a harsh and demanding master. In more temperate climes, he's more likely to be viewed benevolently, as a bringer of clement weather and bountiful harvests. In hotter regions, folks shake their heads knowingly, and watch their own crops go sere with Moloch's displeasure.
Human sacrifice, especially of slave children, has been strongly associated with Moloch's worship in the past. In most Terrasan regions today, this is no longer practiced.
Culsans (CULL-sans) - While never openly worshipped, this god of thieves is very commonly given a quick prayer by the land's many less than upstanding citizens. Also known as Frezur Blue as a nickname (origin unclear), many invoke his name only to make fun of it, and ask what part of him is blue (usually with a randy joke about his sex life) which causes the priests of Ashtarte or other more learned theologians no end of frustration. They simply roll their eyes, comment that "Blue" in this case is merely a mispelling of his proper name anyway, and although Culsans may seem to be an easy-going god who doesn't mind a few jokes made at his expense, only the truly foolish think that it is wise to upset the god who can take away everything that they own, and even steal their very souls.
Many other gods exist, but these are the ones that are most important and that everyone will know.
With thanks to Green Ronin; this bears obvious similarities to the deities of The Pirates Guide to Freeport, mingled with the demonic pantheon showcased in Armies of the Abyss. Also thanks to the Etruscans, Canaanites, Elamites, ancient Slavs and ancient Romans. You guys rawk, dudes!