Here is the full list of all 40 Empires in Ruins achievements.
Finish the campaign in easy mode
Develop 3 Soldiers&Builders Tier 5 technologies
Develop 3 Resources&Building Tier 5 technologies
Develop 3 Towers Tier 5 technologies
Set aflame an enemy covered in oil
Fight and finish 100 battles
Conquer the whole map in Sandbox mode
First 20000 kills
Collect 5 Gold Medals in Arcade (3 stars battles in Hardcore mode)
Successfully prevent one event in a province
Finish a campaign without losing a single battle (Autoresolves don't count)
Finish the campaign in intermediate mode
Don't skip a single dialog during a campaign run
Build and unleash your first Bombardier
Kill 1000 enemies with artilleries
First 5000 kills
Upgrade a settlement to Fortress
Hang 3 governors
Upgrade a settlement to Town
Complete the main tutorial
Kill 10 enemies with a single Call the Charge! ability use
One tower achieves 100 kills in a single battle
First 100 kills
Win one battle in intermediate mode building only 2 towers.
First kill
Build one of each of the buildings available in the game
Build one of each of the towers available in the game
Finish the campaign in Hardcore mode
Beat all the 26 base arcade maps in Easy mode
Beat all the 26 base arcade maps in Intermediate mode
Beat all the 26 base arcade maps in Hardcore mode
Have a Soldier die while under the effects of Martyrdom and running out of enemies