Here is the full list of all 12 The Depths of Tolagal achievements.
Make it through the old garrison
Make it through the forest
Defeat the Ashdurbuk
Defeat the Hydra
Defeat the Maugoth
Get killed by a spike trap
Make it through the buurzlug
Make it through the deep moot
Make it through the summoning rooms
Kill 2 enemies in the same turn
Kill 3 enemies in the same turn
Kill 5 enemies in the same turn