Here is the full list of all 21 Warlocks vs Shadows achievements.
Finish the tutorial
Kill boss of the Greenlands
Kill boss of the Industrial Wasteland
Kill boss of the Swampland
Kill bosses of the Frozen Lake
Kill boss of the Shadow World
Do not skip credits
Deal 10k damage
Deal 50k damage
Deal 100k damage
Deal 500k damage
Deal 1 milion damage
Cast 1k spells
Cast 5k spells
Cast 10k spells
Cast 20k spells
Cast 50k spells
Open all chests
Finish without deaths
Play 10 duels
Play every Warlock