Here is the full list of all 18 A Timely Intervention achievements.
Artifact Defeated
All Along the Watchtower
25+ Secret Rooms Found
A Timely Intervention
Secret Passage Found
12+ Sidequest Completed
All Stonebarrow Lake Foes Killed
Underworld Demon Defeated
Ancient Crypt Found
Argmahn Defeated
Borehole Worm Defeated
6+ Sidequests Completed
5000+ gold
Frost Dragon Defeated
Troll Defeated
1000+ gold
Orc Leader Defeated
Hydra Defeated