Here is the full list of all 12 The Depths of Tolagal achievements.
Make it through the forest
Defeat the Ashdurbuk
Defeat the Hydra
Defeat the Maugoth
Get killed by a spike trap
Make it through the old garrison
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