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