The Hounds of the Morrigan

All who are true creatures will help where they can. As to the hounds, when they hunt--do not run.

The Hounds of the Morrigan is a fantasy novel from 1985, written by Pat O'Shea. It's big, it's whimsical, and it contains more references to Irish Mythology than you can shake a stick at. The very plot itself revolves around the Celtic Goddess of War trying to absorb an ancient demon into her soul so that she becomes unstoppable.

Pidge--Patrick, in full, but everyone calls him Pidge--is an ordinary-if-bookish ten-year-old boy living in the Irish countryside with his little sister, father, and aunt. One day, while biking through the city, he stumbles upon an old book shop and finds an ancient tome. On one page is a drawing of a horrible serpent, the very image of which itself fills him with dread. Meanwhile, one of his neighbors rents out his spare greenhouse to a pair of wild old women who ride around on motorcycles, who claim to be artists. The two are indeed related: That night, Dagda, the God of all that is good, tells him that the book contains the serpent Olc-Glas, a horrible beast imprisoned there long ago. The two old women are Macha and Bodbh, and are part of the Morrigan--the Goddess of War and Discord and Death herself. They are out looking for the serpent themselves, because, if they add his poison to theirs... Well.

Olc-Glas is too powerful to be dissolved by anything but the Morrigan herself. But there is a way: Long ago, the great hero Cuchulain spilled a drop of her blood onto a pebble. If they can find that pebble, with its single drop of blood, they can use it to destroy Olc-Glas. But if The Morrigan finds it first, not only will she stop them from destroying the serpent, she'll get him for herself.

The Dagda chooses Pidge and his little sister Brigit to find it, on the grounds that they are brave enough, and clever enough, and alone true enough to do what is right instead of trying to use the serpent's power for themselves. But the Morrigan and her sisters have sent their dastardly hunting hounds after the two siblings, as they brave the world of Celtic myth in search of the stone. Luckily, all creatures good and light are looking out for Pidge and Brigit. But is it enough to keep the hounds away until they can find the pebble and destroy the serpent?

Despite its great (almost 700 pages!) size, the book is told in a lyrical fairy-tale style generally geared at children (and anyone who loves a good yarn). It contains Nightmare Fuel and Sweet Dreams Fuel in equal measure, though it remains firmly on the "idealistic" scale of the Sliding Scale of Idealism Versus Cynicism.

Tropes used in The Hounds of the Morrigan include:

Action Girl: Brigit may only be 5, but she has the heart of a spirited adventurer.
Amusing Injuries: Puddeneen does not like hammers.
Because You Were Nice to Me: Causes Fowler to make a Heel Face Turn.
Best Out of Infinity: The Glomach tries to do that when Brigit beats him at jacks. She won't have any of it.
Bilingual Bonus: A great many if you happen to speak Gaelic. If not, the back of the book provides a handy glossary and pronounciation guide which explains the name meanings, as well.
Boisterous Bruiser: Brigit is this in spirit, if not in actuality.
Butt Monkey: The poor Seargent. Perhaps by nipping into illegal whiskey he's asking for it, but...
Cave Behind the Falls: There's one in the Second Valley that Pidge, Brigit, and Cooroo use to escape.
Cunning Like a Fox: Cooroo, of course.
Deliberately Cute Child: The Morrigan conjures one in order to capture the Seargent.
Development Hell: The book took ten years to write. The author even tried to write a sequel, but it never quite materialized.
Everyone Join the Party: The Seven Maines, Maeve and Ailill (the Weeping Woman and her gander, plus her men who were ducks), Finn and Daire, all their friends, Boodie and Patsy, and Cathbad the Druid.
Everything's Better with Rainbows: The Dagda's gift to Pidge and Brigit after they complete their quest--rainbows just for them, just because, whenever.
Evil Is Sexy: The "main" Morrigan sister is breathtakingly beautiful.
The Fair Folk
Flower Motifs: Daisies are a recurring theme, because they are the flowers of Angus Og, the God of Love.
Food Porn: In writing, as the world of the spirits is so full of tasty treats you'll want to jump in and take a bite yourself. We have specially-seasoned scrambled eggs, sausages abound, wonderful fruits, and even the Swapping Sweets, which are both yummy and useful.
For the Evulz: All three Morrigan sisters. However, they feed off corpses, so causing as much havoc still does serve them.
Funetik Aksent: A number of characters have them.
Getting Crap Past the Radar: Brigit tries to do this with, "Where's that bloody pebble?!" Pidge catches her and gives he a scolding.
Giant Spider: Mawleogs and his clan are a whole family of them! However, they're firmly on the good side, and they love acrobatics and singing songs.
God in Human Form: Boodie and Patsy, who are really Brigit (the goddess) and Angus Og, respectively.
Gorn: The final battle is almost insanely bloody, such that if the book were to be filmed, it would probably get a PG-13 rating at least for that scene alone.
Happy Rain
Hell Hotel: Castle Durance.
Heel Face Turn: Fowler, Because You Were Nice to Me.
Hilarious in Hindsight: The two twins are a pair of squabbling old twins, with big hooked noses, one of which has flaming red hair and the other of which has icy blue hair. If you've played The Legend of Zelda: Ocarina of Time, comparisons to Twinrova will leap to mind.
Hot Amazon: Hannah, one of the people Pidge and Brigit meet. She's a little old for "hot," but she's still rather lovely in her way.
Inn of No Return: The original designs of Castle Durance.
Irish Names: Unless you are Irish, we recommend giving this page a good once-over before reading this book.
It May Help You on Your Quest: Many characters on the side of good give Pidge and Brigit items in this fashion early on.
Kick the Dog: The main Morrigan shows just how nasty she is when she finds a pair of decades-old friends talking quietly by the fire, and causes a horrible argument leading to a teary breakdown between them just because she enjoys sowing discord.
Kid Hero: Pidge and Brigit. Brigit is only 5!
Last-Episode New Character: Raidarc, who is introduced after the Very Definitely Final Dungeon, but sticks with the heroes to the end.
Little Miss Badass: Brigit envisions herself as one.
Loads and Loads of Characters: Pidge and Brigit meet a lot of people on the road.
Name's the Same: Boodie points out early on what a good name Brigit has, because she shares it with a goddess named Brigit. Boodie is that goddess.
Napoleon Delusion: An earwig believes he's Napoleon.
New Powers as the Plot Demands: Justified. The magic walnuts given to Pidge and Brigit explicitly provide them with whatever they might need at the time.
No Accounting for Taste: Hannah and Corny, but this is noted by Corny as applying mostly on wash day. Any other day, Hannah is a perfectly nice lady.
No More for Me: The Seargent keeps blaming his poteen for the weird things he sees happening to him, but keeps drinking it anyway.
Not So Stoic: The Seargent, when his Weirdness Censor starts to fail.
One-Winged Angel: Subverted. The Morrigan sisters' last action is to turn into an immense, vile, three-headed giant crow... but the fight is already done, and it's only to scream their rage at the children before leaving.
Only Known by Their Nickname: Macha and Bodhb are typically only referred to by their in-story aliases, Melodie Moonlight and Breda Fairfoul.
Precision F-Strike: "You're a damned fool."
Quick Nip: The Seargeant tends to nip into his stores of confiscatched hootch for... less-than-professional reasons.
Reality Altering Miniature: The table the Morrigan sisters use.
Road Sign Reversal: The very first trick Macha and Bodhb try to pull on Pidge. It's much eerier than the usual examples, because, of course, they have magic.
Sealed Evil in a Can: Olc-Glas. His release is something they want to prevent.
Sealed Good in a Can: The Irish Elk.
Talking Animal: Most animals in the other world talk. Even the insects!
Team Pet: Cooroo, once he joins the team.
Third Line, Some Waiting: Pidge and Brigit, and the three Morrigan sisters, form the main two plot threads. The Seargeant who gets unluckily caught up in their fight is the third.
Tiny Guy, Huge Girl: Cornelius and Hannah, one couple Pidge and Brigit meet on their journey. Luckily, she's also the fastest runner in the world, and helps them.
Tomboy and Girly Girl: Melodie and Breda are a villainous version, with Melodie being the sweet/romantic one, and Breda being the more blunt one.
Trademark Favorite Food: Cooroo loves sausages.
The Very Definitely Final Dungeon: The Third Valley, definitely. And, possibly, the Morrigan's labyrinth, though Mossie Flynn takes care of that unintentionally.
Victory-Guided Amnesia: Although the Dagda takes away Pidge and Brigit's memories, he favors them after. Cooroo comes back as their friend, though he can no longer talk to them, and Dagda sends them rainbows just for them.
Weirdness Censor: The Seargent attempts to maintain his for quite a while, blaming poteen, before he finally realizes there's nothing he can do.
The World Is Just Awesome: Pidge has a moment of this when he first beholds the second valley.