Book of Mercenaries is a single-player game mode first released on April 6, 2021 with new chapters releasing until March 17, 2022.
It uses a classic linear adventure format with an appearance similar to Dungeon Run screen. Like Book of Heroes, Book of Mercenaries is about telling the journeys and stories, but the main characters are mercenaries, who were first introduced in Forged in the Barrens as legendary cards and unique to Hearthstone.
Like Book of Heroes, Book of Mercenaries featured a chapter for each of the ten classes that existed before Patch 25.0.0.158725, for a total of 80 missions or bosses. It is completely free to play and available to everyone. Additionally, completing a class's story rewards the player a corresponding class pack.
Warrior was the first class and 
Rokara's story was the first story to be introduced. New missions were released over the course of the Year of the Gryphon.
Book of Mercenaries' Choose Hero menu
For general information on adventures, see Adventure.
- Book of Mercenaries consists of 10 classes' stories, each with 8 encounters, for a total of 80 boss encounters.
- The player is given pre-made deck for each boss encounter, controls a special hero with their corresponding Hero Power, and gets special interactions between their hero and boss.
- During a class's story, the player must encounter the bosses in order and cannot choose the specific ones.
- However, if the player loses an encounter, the player can try again without being reset to the first encounter, unlike Dungeon Run or similar modes.
- The player can press the "Retire" button, which is under the player's hero portrait, to be reset willingly.
Boss encounters and characters[edit | edit source]
Below is the list of boss encounters and player characters for Book of Mercenaries.
| Hero |
Date of release
|
 Rokara |
April 6th, 2021
|
 Xyrella |
June 3rd, 2021
|
 Guff |
June 15th, 2021
|
 Kurtrus |
July 13th, 2021
|
 Tamsin |
August 31st, 2021
|
 Cariel |
November 9th, 2021
|
 Scabbs |
November 16th, 2021
|
 Tavish |
February 1st, 2022
|
 Bru'kan |
February 14th, 2022
|
 Dawngrasp |
March 17th, 2022
|
A hero's Book of Mercenaries has been completed
Upon completing a class' story, the player can claim a corresponding class pack. As soon as the player defeats the final boss of a story, a following note, titled <Hero name>'s Book of Mercenaries, appears:
- <Hero name>'s Book of Mercenaries has been completed. Celebrate with a new card pack!
- Main article: Book of Mercenaries boss cards
In addition to the collectible cards from card sets, Book of Mercenaries brings many unique cards, Playable Heroes, Hero Powers and many more available only during the boss encounters.
- Blizzard Entertainment (2021-04-06). Meet the Mercenaries. PlayHearthstone. Retrieved on 2021-04-08.
Patch 20.0.0.77662 (2021-03-25): Added.
