First posted February 2026.

It’s been a while since the last time I spoke about using mythology in TTRPG storytelling – for transparency, I have a few players here so I try not to talk about anything before we get to it in-game so as not to spoil anyone. But as we approach the end of Fantasy High’s freshman year arc, I can finally talk about some of the mythology that’s gone into the planning of it, including a wholly fabricated myth I wrote and wanted to share here.

One of our player characters is a cleric of The Morrígan, and another is a dragonborn with a Welsh name. With those two in the mix, I knew I’d be playing with some Celtic mythology. I’ve been playing fast and loose with both Irish and Welsh traditions – while Ipheon’s patron The Morrígan comes from the Irish tradition, her parents’ patron is Arawn from the Welsh. In the wider Celtic folklore, the Otherworld is a unifying feature which allows me to cross the mythological streams, so to speak. In the Irish tradition it’s called Tír na nÓg, and in Welsh it’s Annwn, but both terms refer to the same place, or at least places with such similar descriptions as to be syncretic.

The Otherworld – an afterlife location – is especially useful in the world of Fantasy High. Our own Fantasy High campaign takes place in a kind of parallel universe to the Fantasy High of Dropout’s Dimension 20 series. The series canon uses the Nine Hells as a frequent destination and a major player in the events of the players’ lives. Likewise, in our campaign, the afterlife is very present: a tiefling whose mother works in one of the Hells, the child of funeral directors who themselves are grave clerics, a witch goddess trapped in one of the Hells and a player’s ex-adopted family member plotting to free her.

In crafting the A-plot for freshman year, I looked at ways to connect all these disparate threads using mythology. I liked the complicated relationship between The Morrígan and the legendary hero Cú Chulainn, neither benevolent nor antagonistic. I couldn’t quite make the leap between Cú Chulainn and the Otherworld, though; there aren’t any significant myths about him visiting Tír na nÓg.

There are myths about a Silver Branch being the key to entry into the Otherworld, but none of them were especially appealing as reference stories to play with. Thinking about it from a game perspective, you don’t want to give the players anything overpowered, or that makes the game too easy. While I thought of the Silver Branch early on in the planning process, I tried really hard not to use it because I felt it would be too simple and make the players’ solving of the puzzle of getting into the Nine Hells unsatisfying. I didn’t want it to be too easy to come and go from the Nine Hells, so simply giving them this item felt like a bad call.

But I ended up doing it anyway! Here’s how I managed it.

In myths about the Silver Branch (and the Roman equivalent, the Golden Bough), it’s connected with aid and pleasure – it’s bestowed by helpful or enticing figures, and the Otherworld its users reach is pleasant. I wanted it to become something less positive in our story – something that’ll get you where you’re going, but that doesn’t ease the journey. To that end, I made up a myth which the players discovered in a book they found in a temple. It’s certainly inspired by stories of heroes travelling to and from lands of the dead, and takes as its starting point a real Irish myth, but the following story appears in no Celtic mythological sources.

Cú Chulainn was challenged to a duel by a mysterious young man – not an uncommon occurrence for a legendary hero. And in the battle, Cú Chulainn was victorious – again, not uncommon. But what was uncommon about this fight was that the young man who lay dying revealed with his final breaths that he was the son of Cú Chulainn.

The hero grieved for the son he never knew, the son who had died by his own hand. Despair and melancholy overwhelmed him, and he neither slept nor ate. Finally, he sought guidance from his father, the god Lugh. He begged for anything that could ease his pain. Lugh offered him a Silver Branch, which would grant passage to the Otherworld. However, Lugh warned Cú Chulainn that the branch would take him to whatever or whoever within the Otherworld he was most closely connected to. Considering he’d never known his son, it was unlikely the branch would lead him there. Nevertheless, Cú Chulainn was certain nothing in the Otherworld would be closer to him, and he took the branch.

He searched a nearby forest for a tree with a broken branch which he could attach the Silver Branch to. Tendrils of silver mist coiled from the branch and held it in place on the tree’s broken branch stump, and suddenly Cú Chulainn found himself not in the forest he’d just been in, but one filled with golden light and perfect, beautiful trees. Birds sang all around, and he heard footsteps running towards him. He turned and saw – Cú Chulainn.

The hero now known as Cú Chulainn was born Sétanta. Culann the smith invited Sétanta’s father to a feast, and Culann’s guard dog was accidentally set loose on the boy. Though he killed the dog in self defence, he still owed the smith a replacement. He offered himself until a suitable dog could be raised to replace the one he killed, and thus he became known as the Hound of Culann: Cú Chulainn.

Here in the Otherworld, the man once known as Sétanta looked down on his namesake, a happy dog with a stick in his mouth and a wagging tail. Undeterred, he searched the beautiful forest for his son, but to no avail. When finally he was exhausted and defeated, he took the Silver Branch down from the tree, and returned to the world of the living.

This framing had the effect on my players I hoped for – immediately, they began planning who should be the one to actually place the branch, hoping to avoid being attracted to anyone they didn’t wish to see. The warlock whose patron was having some trouble in the Bottomless Pit was chosen to attach the Silver Branch, but unfortunately the patron’s prison guard was, after all, the tiefling’s estranged mother, who’d abandoned her son in the mortal world in order to pursue a promotion to Pit Fiend.

What were the odds. :)

Speaking of improbable odds, there’s a door to Annwn straight from the Bottomless Pit, and that’s where our heroes find themselves now – a forest as dark as Cú Chulainn’s was light. Something’s definitely not right here; the hounds of Annwn have been heard barking the alarm throughout the Nine Hells, and word of something amiss in the Otherworld has made it to the mortal plane. The darkness may or may not be connected to the shrieks of an imprisoned being somewhere just out of sight...whose cleric just attacked his own adopted niece.

I think I’m more pleased with myself for writing the myth than anyone else, but what is this platform for if not tooting my own horn.