Here is the full list of all 33 The Iron Oath achievements.
Obtain a Named item
Reach a Renown Level of 5
Hire 10 recruits during a campaign
Survive the battle to save Andilon during the prologue
Fully explore a dungeon
Finish the Prologue
Kill your first Boss
Win a battle without taking any damage
Kill an Elite enemy
Kill 50 Elite enemies
Kill 20 Bosses
Kill 500 enemies
Kill 1000 enemies
Win 100 battles
Have a character kill 3 enemies in a single turn
Reach Level 10 with every class
Have one character reach Level 20
Unlock all enemy Codex entries
Reach a Renown Level of 10
Reach a Renown Level of 20
Reach day 1000
Complete the 'Strength in Numbers' campaign mission
Finish the Campaign
Help the Vanguard retake Wealden
Participate in the final battle during a Scourge Crisis and save the city
Unlock and travel to the region of Dragate
Visit every city
Obtain a Legendary item
Obtain 5 Legendary items
Amass 15,000 coin at once
Find and interact with every Shrine
Unlock all jobs
Obtain all Journal entries from every region