Here is the full list of all 21 Caveblazers achievements.
Achieve 100% game completion
Finish the game in co-op mode
Complete 10 levels with both players alive in co-op mode
Reach the Forsaken Jungle in co-op mode without dying
Complete the game with all 5 relics active
Reach the Shrouded Land
Defeat a boss with all 5 relics active
Revive a friend
Create a mega shadow weapon
Discover all 5 relics
Fill up the monsters section of your journal
Finish the game
Play for a total of 20 hours
Drink 100 Potions
Defeat all of the regular bosses
Create a super weapon
Become the champion of an arena
Defeat a boss
Finish the tutorial
Kill 100 enemies
Smash 50 treasure chests