Here is the full list of all 24 King Erik achievements.
Collect 500 coins.
Complete the Coastal Fortress levels.
Capture your first soul in to the scepter.
Kill an enemy by luring them into a pendulum blade for the first time.
Collect 300 coins.
Complete the Highlands levels.
Best Duke Lukion in your first encounter with him.
Lure an enemy to their death by contraption.
Your first kill!
Complete the Forest Fortess levels.
Complete the Swamp Fortress levels.
Complete the Inlet Fortress levels.
Complete the Desert Oasis levels.
Complete the River Fortress levels.
Complete the Warchester levels and defeat Duke Lukion!
Kill 30 Saxon Soldiers.
Kill 60 Saxon Soldiers.
Kill 100 Saxon Soldiers.
Kill 200 Saxon Soldiers.
Collect 1000 coins.
Kill 5 enemies by luring them into a pendulum blade.
Kill 10 enemies by luring them into a pendulum blade.
Execute Duke Lukion after his defeat.
Spare Duke Lukion's life after his defeat.