Here is the full list of all 21 FIVE: Guardians of David achievements.
Complete Act 1 Storyline
The mighty Goliath has fallen!
Defeat the Lion on a snowy day
Complete Act 2 Storyline
Complete Act 4 Storyline
Complete Act 5 Storyline
Complete Act 6 Storyline
Complete Act 7 Storyline
Complete Act 8 Storyline
Complete Act 9 Storyline
Complete Act 10 Storyline
Complete Act 11 Storyline
Defeat Neziah
Defeat Ishbi-Benob
Defeat Genubath
Defeat Seirath
Defeat Tahrea & Melech
Defeat Barakel
Defeat Shobak
Defeat Sethur
Defeat Zaham