Here is the full list of all 91 Ultimus bellum achievements.
Collect 15 stars
Collect 30 stars
Collect 50 stars
Collect 100 stars
Collect 250 stars
Finish all easy levels on Act 1
Finish all medium levels on Act 1
Finish all hard levels on Act 1
Finish all impossible levels on Act 1
Finish all nightmare levels on Act 1
Finish all easy levels on Act 2
Finish all medium levels on Act 2
Finish all hard levels on Act 2
Finish all impossible levels on Act 2
Finish all nightmare levels on Act 2
Collect 1 or more stars
Click on the tree 5 times
Click on the tree 25 times
Click on the tree 50 times
Click on the tree 100 times
Enough to click, it's time to save the world
Robin earned 5 level
Robin earned 10 level
Robin earned 15 level
Robin earned 20 level
Robin earned 25 level
Jaina earned 5 level
Jaina earned 10 level
Jaina earned 15 level
Jaina earned 20 level
Jaina earned 25 level
Ivan earned 5 level
Ivan earned 10 level
Ivan earned 15 level
Ivan earned 20 level
Ivan earned 25 level
Ragnar earned 5 level
Ragnar earned 10 level
Ragnar earned 15 level
Ragnar earned 20 level
Ragnar earned 25 level
Jack earned 5 level
Jack earned 10 level
Jack earned 15 level
Jack earned 20 level
Jack earned 25 level
Liu earned 5 level
Liu earned 10 level
Liu earned 15 level
Liu earned 20 level
Liu earned 25 level
Upgrade shop to level 2
Upgrade shop to level 4
Upgrade shop to level 6
Upgrade forge to level 2
Upgrade forge to level 4
Upgrade forge to level 6
Finish all easy levels on Act 3
Finish all medium levels on Act 3
Finish all hard levels on Act 3
Finish all impossible levels on Act 3
Finish all nightmare levels on Act 3
Finish all easy levels on Act 4
Finish all medium levels on Act 4
Finish all hard levels on Act 4
Finish all impossible levels on Act 4
Finish all nightmare levels on Act 4
Merlin joined you
Merlin earned 5 level
Merlin earned 10 level
Merlin earned 15 level
Merlin earned 20 level
Merlin earned 25 level
Howard joined you
Howard earned 5 level
Howard earned 10 level
Howard earned 15 level
Howard earned 20 level
Howard earned 25 level
Thrall joined you
Thrall earned 5 level
Thrall earned 10 level
Thrall earned 15 level
Thrall earned 20 level
Thrall earned 25 level
Azazel joined you
Azazel earned 5 level
Azazel earned 10 level
Azazel earned 15 level
Azazel earned 20 level
Azazel earned 25 level