plagued by design.

Heliod was the god of the sun, and was supposed to be the patron of justice and heroes. In reality he was a paranoid narcissist who thought he should be the only god on Theros. He set Gideon up for failure, murdered Elspeth out of jealous, and brainwashed Daxos into becoming his chosen killer. Notably, Elspeth defeated him in single combat, and Erebos was so amused, he let her out of the Underworld. Heliod died during the Invasion after being compleated; thankfully, Kaya the Ghostwalker ended him.

Erebos, the god of the dead, is no better than his brother, petty and vindictive, tormenting the people in the Underworld until their memories fade and they turn to nothing. He tortured Elspeth with a vision of what her life on Bant could have been, betrayed the boon he owed her by returning Daxos as a memory-less zombie, and murdered all of Gideon’s friends after Gideon threw Heliod’s spear at him.

Nylea is the goddess of the wild places, and a good friend of Elspeth and Daxos.

She also gay as hell.

Pharika is the snoddess (snake goddess) of both poison and medicine. She's cold, calculating and uses everyone and thing to experiment buuuuuuut:

Karametra is the harvest goddess, and Nylea's long suffering sister. She is the patron of Setessa, the all-female, Amazonian inspired polis.

Thassa is the sea goddess, turbulent and moody. She is not a fan of planeswalkers after Kiora of Zendikar literally stole her identity. And some of her krakens.

Keranos is the storm god of sudden insight. Also moody. Likes to use death by lightning.

Purphoros is the god of the forge and fire, and is: moody af. When in doubt, set the volcanos off.

Ephara was the one god who wasn't complaeted in the Invasion, and was in charge of the resistance during the Invasion. She is the patron of Meletis, the Athens of Theros.

Iroas is the god of victory, who is locked in eternal stuggle with Mogis, the god of slaughter.

Athreos is the ferryman of the dead, and hates his literal deadend job. During the Invasion, Athreos released Kroxa, the titan of death's hunger, to handle the phyrexians, sending his three headed dog with the titan to monitor the situation. This strategy worked, but the Kroxa is still at large. The dog in question:

Phenax was the first mortal to escape from the Underworld, and became the god of lies, deception and the Returned- the other mortals who have escaped the Underworld by following his path. The Returned are sapient undead who have lost their identities in exchange for their freedom- their memories form separate entities known as eidolons, while the Returned themselves operate purely on instinct, habit, and their muted emotions. Erebos and Athreos particularly hate the Returned, as they're insulting to their existence.

Kruphix is technically the guy in charge here, as the eldest and the god of time, mysteries, and horizons. He can summon the other gods and force them to stay in their starry heaven (Nyx), and out of meddling in the mortal world, if he thinks they're overdoing it. He is very worried about the planeswalkers and the things the planeswalkers fear. He's incredibly difficult to get in touch with.

Klothys is the other eldest, the goddess of fate and destiny. After Elspeth killed a usurper god, the revelation that the gods were replaceable/could be killed caused an uprising among them, and in the chaos, more souls than ever slipped past Erebos's grasp and back into the world of the living. Klothys was enraged, and sent agents of fate to round them up; she created a specific Nyxborn masterpiece to handle Elspeth herself: Calix, the Fatehand, who cannot rest until she is returned to her place in the tapestry of fate, and who sparked to chase her across the planes.

Heros

Daxos was born with a unique gift; unlike other oracles, who only hear the voice of one god, he can hear the voices of them all- making him a rare prize amongst the pantheon. As a child, his mother died to save him from Erebos's clutches, and right after, the boy Daxos encountered a strange girl in the woods, who claimed a sword that fell from the heavens before vanishing again.

Daxos grew up and was claimed by Heliod as an oracle- though Daxos never got a choice in the matter.

Elspeth came back as an adult, magic sword Godsend in hand, and under Daxos's tutelage in all matters Theran became the champion of Heliod and Savior of Theros.

Directly after they consumated their relationship, Elspeth was striken with insanity magic, went berserk, and killed him. He saw it coming through his oracular powers, and forgave her ahead of time.

Elspeth bartered her life for his with Erebos, but Erebos tricked her- sending Daxos back as a Returned, who only endlessly searched the earth for her, remembering nothing else.

When Heliod declared war on the other gods, he picked a champion, and raised Daxos to demigod status, and wiped his memory completely.

Elspeth ended up fighting and having to kill him again- even with his memories restored, as Heliod was controlling his body- to finally have a crack at Heliod himself, and escape the Underworld.

Elspeth thought he's dead, but the comics indicate he escaped the Underworld afterward; then Ashiok told her in their letter that Daxos is still wandering- mindless by day, tormented by her memory at night. But their lying ass could be lying about that.

Elspeth is now an archangel, is famous on Theros for many, many things, and has never gotten a break in her entire life. Here she is, god slaying, which at this point is just like, a Tuesday for her.

Tymaret, the Murder King, is a Returned and a demigod of Erebos. His specific mandate is that he's supposed to find and kill Phenax, to put him back into the Underworld where he belongs. Tymaret has deeply misunderstood the assignment, and decided that he's going to just murder everything in his path, as logically he'll eventually have to kill Phenax. Right?

Kytheon Iora, later known as Gideon Jura, was a Champion of Heliod, who in his hubris, threw the Sunspear at Erebos. Erebos returned it to sender, killing all of his friends, and in his pain and despair, he sparked. Gideon spent the rest of his life trying to make up for his sin, ultimately sacrificing himself to free the one person he'd always believed could save them all (even when everyone else did not).

Gideon died on Ravnica, and as such did not enter the Underworld on Theros. He does have a memorial statue there, where his friends held a funeral. (The woman who actually did save them all, that he died for, was not invited.)

Here's the statue, I believe its in Kytheon's native mountainous Akros, the Sparta of Theros.

Anikthea is a demigod of Erebos, from the Amazonian inspired city of Setessa. As a "reward" for her tremendous skill, she fights at the gates of the Underworld eternally, protecting Setessa from the unceasing hordes of the undead that might break through and threaten the city if she ceases, in exchange for a promise that when Setessa needs her most, she can finally go home.