Here is the full list of all 12 Sword Legacy Omen achievements. It takes around 8-10 hours to unlock all of the achievements on Windows.
Complete Act 3: Chapter 4.
Complete Act 3: Chapter 3.
Complete Act 3: Chapter 2.
Complete Act 3: Chapter 1.
Complete Act 2: Chapter 4.
Complete Act 2: Chapter 3.
Complete Act 2: Chapter 2.
Complete Act 2: Chapter 1.
Complete Act 1: Chapter 3.
Complete Act 1: Chapter 2.
Broken Britannia awaits you!
Complete Act 1: Chapter 1.