Northland Trilogy

Hazel May is a girl who on her fifteenth birthday learns that some members of her family have an ancient ability to travel to another world while they sleep. Guided by a mysterious old man and a growing group of friends, she travels the "Other Side", the source of dreams and myths, searching for a mysterious object that may be the World Tree or the Sampo. However, the Maia family has not been searching for as long as one other creature...

The "parts" are:

Book 1:

Rune Singer
Exile
Northern Man
Erilaz

Book 2:

The Shaman
Claybody
Silent Water

Book 3:

Seax
Firebird
The Compass Rose

Tropes used in Northland Trilogy include:

Action Girl: Laika, to a certain extent.
All Myths Are True: Sorta. The Other Side is implied to be the source of all myths, but most of the forms known on the Wakeside are garbled.
All Trolls Are Different: And there seem to be several different species.
Angel Unaware: Cang Long.
Animal Motifs: Laika- Wolf (Justified in-universe), Otsi- Bear, Hazel- Corbies.
The Apprentice: Hazel, to Otsi at first, and temporarily to several others.
The Archer: Skadi.
Attempted Rape: Not a serious threat to Laika.
Badass Bookworm: Hazel
Badass Family: The Maia family.
Badass Grandpa: Otsi
Bar Brawl: Used quite seriously in Northern Man.
Battle in The Centre of The Mind: Technically, all of the Other Side
Bawdy Song: "Janka se Sirram" is implied to be this.
Big Bad: Lazarus
Big Friendly Dog: Paavik
The Big Guy: Moddi.
Big Damn Heroes: Cang Long and the Chinese army.
Big Eater: Laika
The Blacksmith: These guys are useful for more reasons than one.
Blood Knight: Red Tom.
Blue Eyes: The Thin Man, of all things. And Cang Long.
Boisterous Bruiser: Prince Svyatoslav.
Born in the Wrong Century: Red Tom Couleton has aspects of this.
The Chessmaster: Thaka, in the Wolf council. For a start, she isn't blind, and has been observing a lot of Skee-ga's shenanigans for most of the series; she devises a plan to help Otsi and Hazel against Red Tom; and she uncovers TWO Lazarus incarnations, once by causing Skee-ga to report to it while being followed, and once by manipulating him into revealing it to save his own skin.
Chekhov's Gun: Red Tom's BFS.
The Chosen One: Averted. Hazel is nothing special; she just happens to be the Maia family representative at the time when stuff gets real.
Common Tongue: Seems to exist. No Double Sider has trouble understanding any language on the Other Side.
Cool Big Sis: Laika, to Hazel, for the first few years.
Cool Old Guy: Otsi
Cloudcuckoolander: Drake, though how much of it is real is debatable. His answer is: "All of it, by choice."
Cute Little Tusks: Iningizimu
Dark Is Evil: The Snake-woman. Averted with Corvax.
Dead Person Conversation: Played with.
Deal with the Devil: While supernatural creatures are able to use magic, the only way for humans to use magic is to have "dealings with spirits," which, as Otsi puts it,"You'd have to be a complete bloody loony to do." Doesn't stop some people...
The Dragon: Jakosh Merkana is this to Skee-ga for a while. He eventually becomes the real leader, in all but name.
Do You Trust Me?: Hazel, to Sabkai, as she genuinely likes him and wants to help. He ends up trusting her, and vice versa, but she is ultimately unable to help him.
Erudite Stoner: Drake slips into this role once or twice.
Enemy Mine: Happens quite a bit when Lazarus is in the picture.
Everything's Worse with Bears: The Lazarus Symbiont takes this form, along with Glowing Eyes of Doom. So does Shash.
Evil Is Not a Toy: Stupid, stupid Skee-ga.
Fantasy Counterpart Culture: Every culture has one, that is very similar to its ancient form.
Find the Cure: Sabkai wants to do this, though he realizes all along that his chances are slim.
Fond Memories That Could Have Been: Hazel discusses this with Drake after his death.
Freudian Excuse: Sav Mav se Sirram.
Freudian Trio: Hazel is the superego, Laika is the Id, and Otsi is the ego.
Functional Magic: A part of everyday life on the Other Side. Unusually, not one of the main characters uses it, as it is the exclusive prerogative of magical creatures..
Full-Name Basis: Shan Tasa Aidahan, though not out of respect.
Genre Savvy: Hazel becomes this, due to her role as Badass Bookworm. All of her studies help her to recognise what is going on. She still is fooled occasionally, even towards the end.
Gotta Catch Em All: Averted: they simply need to find many clues to the location of the Sampo because it is hard to find. There is no set number of objects needed.
Grim Up North: Averted. While the North is harsh and cold, it is the homeland of virtually all the characters, who know how to survive and love it.
Holy Hand Grenade: One way of getting rid of the Lazarus.
Honorable Elephant: Iningizimu.
Hot-Blooded: Laika. She, however, does not have a...
Hair-Trigger Temper: Otsi.
Human Sacrifice: Several graves the gang come across contain "these poor buggers.
Husky Russkie: Prince Svyatoslav.
An Ice Person: One of Lazarus' incarnations, the Thin Man. And Skadi.
I Ate What?: Happens a few times. "REINDEER PISS?
I Am Who??: Hazel's grandparents never had the ability to go to the Other Side, and, resenting this, they never told her parents. Hazel thus grew up unaware of her Maia heritage. As a result, her mentor and only living relative on the Other Side is Otsi, her great-grandfather.
I Don't Want to Die: Sabkai.
I Gave My Word: Honour is VERY important to Laika's bunch. Justified in that if your word is not widely accepted, you are not likely to live long, as no one will have dealings with you.
I Know Your True Name: A major fear for most of the characters, as magic and hexes can be made using real names. As a result, most double-siders use a false name, except Drake.
I Need a Freaking Drink: "Someone pushed something into my hand: something warm and alcoholic, bless them."
Indy Ploy: Drake's entire plan to impress Prince Svyatoslav. The Prince is perfectly aware of what is going on, and it is in fact Drake's ability to think on his feet that impresses him.
Insane Equals Violent: The sea captain in Northern Man.
Junkie Prophet: Quite a few of the shamans.
Jumped At the Call: Hazel. Probably Laika too, but we never learn...
Killed Off for Real: Drake. Sabkai. Jackass Merkana. Argus. Red Tom (Maybe.)Skee-ga.
King in the Mountain: Antero Vipunen.
Knife Nut: Laika is the most prominent, but she is far from unique.
Knight Templar: Red Tom Couleton is a mild case.
Lie to the Beholder / They Look Like Us Now: Lazarus
Loophole Abuse: Laika uses this to justify her assisting Hazel and Otsi against Red Tom Couleton. As it turns out, this is exactly what Argus, the Wolf chieftain, actually wanted her to do.
Magical Native American: Shash. At least, this is how he chooses to appear.
Magic Music: The Rune singing.
Maybe Magic, Maybe Mundane: Is the old woman in the forest Baba Yaga? We will never know.
Meaningful Name: Used deliberately in-universe by many double-siders.
Mood Whiplash: In Firebird, a typical Drake moment ("Did you just serve him RAT?")is followed a few minutes later by Drake being mortally wounded.
Never Found the Body / No One Could Survive That: Red Tom.
Never Mess with Granny: The 300-year old Volva.
The Nicknamer: Otsi.
Noodle Implements: The carrot and the two bowls.
Noodle Incident: The fire in Reykjavik, and what part Laika played in it.
Not Quite Dead: Otsi. In an unusual case, he never "died," and was active in the story for a long and unbroken period of time before rumours of his death appeared. Also Drake, to a certain extent.
Obfuscating Stupidity: Again, Drake.
Otaku: Red Tom Couleton, for his adoptive tribe.
Our Liches Are Different: The titular Shaman, for a start. And Koschei the Deathless.
Playing with Fire: Lazarus, in the Furnace Man incarnation.
Pyromaniac: No, not the pitch-black metal man who bleeds fire. Drake Firebrace.
Ralph Wiggum: The Trolls That Sort Rocks.
Reptiles Are Abhorrent: The living Snake tatoo on the Lazarus Woman
Sacred Hospitality: An important plot point, when Laika, a virtual prisoner euphemistically called a guest, declares a stranger to be under her protection. It works, but only because Laika is a respected Badass.
Sanity Slippage: Skee-ga, as a result of his dealings with Lazarus.
Shout-Out: The Trolls argue over what to do with the heroes.
Single-Minded Twins: Alexis and Sasha. They even use only one alter ego between the two of them.
The Smart Guy: Hazel. She has to be.
Smart People Play Hnefetafl: And chess too, when it exists.
Snarky Narrator: Hazel
Speak of the Devil: Lazarus is a nickname. Nobody uses its real name.
The Spock: Hazel
Stealth Pun: Mikki the Finn is always referred to as "Mikki" or "The Finn."
The Stoic: Skadi, Cang Long, Iningizimu, and Shash. Makes Sense.
Squick: The reindeer urine, for a start.
The Dung Ages: Played with. Hazel has to learn to live with dirt, but people do seem to keep reasonably clean, as ancient Norsemen actually did.
Thirty Xanatos Pileup: Claybody. Hazel and Otsi want to investigate old tombs. Red Tom want to force them to fight his neighbours. Using magic, which they don't have, and they don't want to let him know that. Laika wants to rescue them, but can't communicate with them or the Council. Skee-ga wants to kill Laika and break Hazel and Otsi out himself, in order to force them to find clues for Lazarus. Merkana wants to off Skee-ga. Lazarus is Biddy's assistant. And everybody's plans go haywire when the Irish show up.
Took a Level in Badass: Shan Tasa Aidahan. He seems a weakling and useless, then he kills Jackass Merkana. Unusually, his badass deed is mostly a fluke, and inspires him to try harder rather than suddenly proving him a badass.
Totally Radical: Drake exclaims "Duuuuuude!" ("with at least 6 yoos")in front of Prince Svyatoslav, leading Hazel to collapse in a fit of nervous laughter.
Unwitting Pawn: Skee-ga, for Lazarus.
Unresolved Sexual Tension: Laika and Drake
Verbal Tick: Hazel uses a lot of brackets. However, this is her and not the style, as when other characters narrate a chapter or large part of one, they do not.
Wartime Wedding: Corvax and Wulver.
Weirdness Censor: All of the main characters, particularly Drake, take advantage of this gleefully.
World Tree: Yggdrasil, of course. The Sampo is the same thing. So is the Celtic triskellion sign. (It's complicated.)
World of Badass: Averted.
Worthy Opponent: Jakosh (Jackass) Merkana. Also Sabkai, when he happens to be on the other side.
Wretched Hive: Hazel and Co. visit many of these, though the Other Side is far from a Crapsack World.
You Fool!!: One of Otsi's favourite expressions.
You Have Outlived Your Usefulness: Skee-ga, to Lazarus.
Your Mind Makes It Real: Somewhat. Scars and injuries do not carry over much, but death has a delayed reaction: if you die on the Other Side, you are really dead within a year or so.
Zany Scheme: Drake makes a lot of these, one of the most notable being the plan to produce Hammerspace.