This guide contains spoilers for the story, so I only recommend you to use it in case that you already finished the game and have difficulties getting some achievements.
Also, I won't be giving exact, step-by-step instructions, but rather tips to guide you in the right direction. If you still can't manage to get any particular achievement, feel free to leave a comment below.

People of the Steppes
Play as a Nogai.


Coastal Life
Play as a Chukchi.


Clan of the Great Bear
Play as a Khanty.


Reindeer People
Play as a Saami.


Songmaster
Play as a Nivkh.


These five achievements are pretty self-evident. You can get them in the chapter Fever Dreams.

Multicultural
Play as every ethnicity.


Once you get all the five above-mentioned achievements, you unlock this one.

Happy at Home
Become close to your family.


You need to have a good relationship with your family (Family attribute). Just focus on your family in the first three chapters.

Friend to the Small
Become good friends with your animal companion.


Take good care of your animal companion. Getting the Grey Wolf to join you in the chapter On the Road worsens your relationship.

Awooooooooo
Befriend the Grey Wolf.


The easiest way to get this achievement is to choose the feat of compassion in chapter 2.

Adventure Buddies
Befriend the bogatyr Marya Morevna.


Visit her tournament once you are in Kiev, show humility and honesty, don't break your promise to her and give her Koschei's Death. Having the Grey Wolf as a friend also helps.

More Ale
Befriend the bogatyr Ilya Muromets.


Visit him in Kiev, show self-reliance and physical strength, help Svyatogor (go right on the Crossroads). If your animal companion is a frog and your relationship is good, it helps too.

The Spiritual Life
Befriend the bogatyr Alyosha Popovich.


I found this one to be harder to get than the other bogatyrs' achievements.
Visit his religious celebration in Kiev, show humility and intelligence, try to get more expensive lodgings in Kiev. Frightening Baba Yaga with your faith and convincing Koschei's servants to join you help improve your relationships with Alyosha too.
Finally, having a tortoise as animal companion is a good idea in this case.

Status at Court
Meet the bogatyr Dobrynya Nikitich.


Impress the tsar and the tsaritsa with your wit.

Friend of the Old One
Befriend the bogatyr Svyatogor.


Go right on the Crossroads in order to meet Svyatogor.
If you befriended Ilya Muromets during your stay in Kiev, he will give you some useful tips on how to stay awake during Svyatogor's story and not to anger him.
Then you have to convince Lena to come back with you. You must have a good relationship with either your family or Svyatogor, or be very self-reliant, if you want to convince her.

Friend to the Bogatyrs
Befriend all of the bogatyrs.


To be clear, you DON'T need to befriend all of the bogatyrs during the same playthrough (I think it's impossible to do). Just become friends with them one by one, and you will get this achievement.

Go left, when you're on the Crossroads, and complete the three tasks of Baba Yaga.

Bleached Linens
Clean Baba Yaga's sheets.


For the first one you need to either be humble or strong, or have strong ties to your family. But you can also use the item you received from Marya.

Mmm, Refreshing
Bring Baba Yaga a bucketful of water.


You can complete the second task by using trickery or your resources. Or you can ask your animal companion for help.

Fancy That
Collect good vegetables for Baba Yaga's stew.



For the final task you need to be really strong or be friends with the Grey Wolf, but you can also use the Demon Mark.

Considerate Guest
Help Baba Yaga make a nice dinner—that doesn't include you as the main course!


Complete all Baba Yaga's tasks and convince her not to eat you.


Go straight on the Crossroads to meet Zmey Gorynych.

He's Not Very Smart, but…
Defeat Dubynya, a strong dragon from Zmey Gorynych's brood.


Challenge Zmey Gorynych and show your combat prowess.

He's Not Very Strong, but…
Defeat Gorynya, a smart dragon from Zmey Gorynych's brood.


Challenge Zmey Gorynych twice and show great combat prowess.

Biggest Dragon of Them All
Defeat Zmey Gorynych in combat.


Challenge Zmey Gorynych for the third time and show exceptional combat prowess.

Terror of Zmey's Brood
Defeat all the dragons in Zmey Gorynych's brood, including himself.


Challenge Zmey Gorynych three times and win every combat.

Admired by Dragons
Impress Zmey Gorynych so much that he helps you on your quest.


Impress Zmey Gorynych with your combat prowess, wits or pride.


Go right on the Crossroads to meet Svyatogor.

Alert and Ready
Stay awake to the end of Svyatogor's long story.


If you befriend Ilya in Kiev, he will give you useful tips to help you stay awake. If not, just do everything that can help you not to fall asleep: move, pinch yourself, drink water etc. Keep in mind, though, that it will negatively affect your relationship with Svyatogor.

Lovers Reunited
Get Lena and Svyatogor back together.


Convince Lena to come back to Svyatogor by having a good relationship with your family, having a good relationship with Svyatogor or being very self-reliant.





Hero at the Crossroads
Befriend everyone at the crossroads.


Help Baba Yaga with the dinner, impress Zmey Gorynych, reunite Svyatogor and Lena and have a good relationship with Svyatogor.
You can't visit all the places at the Crossroads during the same playthrough, so you will have to play at least twice in order to get this achievement.

Aren't You Clever
Solve the riddle in Koschei's fortress.


You need to answer all the questions correctly.
The riddle is not that hard, if you pay attention to what the others tell you about Koschei.
If you are stuck, the answers are:
The chicken eats the chick eats the egg.
Death
I am a criminal.

You're No Match for My Brains
Find the magical hat in Koschei's fortress.


When there are three paths before you, go left.

You Are the Brute Squad
Find the magical gauntlets in Koschei's fortress.


When there are three paths before you, go straight.

Is There a Village Nearby
Find the magical handkerchief in Koschei's fortress.


When there are three paths before you, go right.

I Am No Thief
Refrain from stealing from Koschei's treasure hoard.


When you are presented with the opportunity to steal from Koschei, choose not to.

It's in Good Hands
Return Koschei's Death to Marya Morevna.


Give Koschei's Death to Marya.

The Death Is Mine
Keep Koschei's Death for yourself.


If you want to successfully keep the Death for yourself, you need to have both pride and wits.

Saboteur
Defeat Koschei with Zmey Gorynych's magical amulet.


Impress Zmey Gorynych at the Crossroads and then give Death to Marya.

Badger-Mole
Survive on your journey beneath the earth.


Don't get killed while travelling beneath the earth. It's not that hard. Just be careful and don't abuse the Demon Mark.

All the Green of Nature
Feed emeralds to the Indrik Beast.


Keep investigating until you get to the emeralds and then, when you are trying to calm the Indrik Beast, feed them to him.

Rubies, Assemble
Feed rubies to the Indrik Beast.


Keep investigating until you get to the rubies and then, when you are trying to calm the Indrik Beast, feed them to him.

It Was Bound to Happen
Feed sapphires to the Indrik Beast.


Get the sapphires and then, when you are trying to calm the Indrik Beast, feed them to him.

Through Dungeons Deep and Caverns Old
Befriend the Lady of the Mountain.


In order to befriend the Lady of the Mountain you need to sing and talk to her. Then, when you get separated, try to rescue her. Your trickery has to be really high, if you want to save her.

Ascend Uhin's Hill
Face three of Uhin's challenges.


Ascend Uhin's Mountain
Face four of Uhin's challenges.


Ascend Uhin's Peak
Face five of Uhin's challenges.


After finally getting to Uhin, you will have to face from three to five challenges. The number of challenges depends on your humility. The humbler you are, the less challenges you will have to face.
You can use the Demon Mark during the challenges, but I don't recommend it, because you risk turning into Uhin's servant.
Here are some tips on each of the challenges:
1) Your mother - you have to either have a very good relationship with your family or a lot of pride.
2) Your friend (it can be your animal companion, the Grey Wolf or Marya Morevna, if you betrayed any of them, or your sibling, if you didn't betray anyone) - you have to be very self-reliant, be very humble (animal companion, the Grey Wolf, Marya), or have a very good relationship with your family (your sibling).
3) Your double - either be very smart or very self-reliant.
4) The tsar and the tsaritsa - you must have a great relationship with your family, or be really weak and inexperienced, or be good friends with Marya, or know the royal family's secret (you can discover it in Koschei's fortress, if you are witty enough).
5) Your family's arms and armor - in order to reclaim them you have to be really strong, have the gauntlets from Koschei's fortress or be very self-reliant.

Indomitable
Pass five of Uhin's challenges and survive your encounter with her.


If you survived five of Uhin's challenges and have a high level of pride, you get this achievement.

Face Your Demon
Face and defeat Uhin.


Deafeating Uhin is not easy at all, because you have to be very strong, very smart and very experienced in combat at the same time.

Hearth and Home
Settle down with your family at the end of the adventure.


Your relationship with your family has to be great, but living in the countryside isn't easy, so be sure to gather as much resources as you can during your travels!

The Seat of Power
Take your place at the Tsar and Tsaritsa's right hand at the end of the adventure.


Surviving in the court is not for the humble. Only prideful people can do it.

The Road Calls Me
Go searching for The Thing That No One Can Find in Whereabouts Unknown.


If you are determined to go on such a dangerous trip, you must be absolutely self-reliant.

Steven Universe
Befriend or impress every character in the game.


Befriend or impress all the bogatyrs, your family, your animal companion, the Grey Wolf, Baba Yaga and Zmey Gorynych.

Spirit of the Forest
Encounter the leshii behind Baba Yaga's hut.

During the third Baba Yaga's task choose the third option, if you aren't friends with the Grey Wolf and your self-reliance is low.

Never Go Hungry Again
Get an ever-full plate of kasha from Baba Yaga.


Have a good relationship with Baba Yaga by helping her with the dinner and then ask for no boon.

Minecraft
Discover the mysterious, perfectly round, disappearing quarry.


To get this achievement you need to play as a Khanty, have a bird as animal companion, go right on the Crossroads and then go in search of Lena.

Stare into the Abyss
Peer into the abyss and catch a glimpse of the horrible Chudo Yudo.


Pretty self-evident. When you are in Koschei's fortress, choose to stare in the Abyss.

These are all the achievements in Demon Mark: A Russian Saga.
I hope you find this guide useful.
Enjoy the game!