Here is the full list of all 21 Necromancer Returns achievements.
Complete campaign mode.
Use Vampirism spell 5 times.
Learn all skills.
Upgrade all units.
Use units’ abilities 20 times.
Win 40 battles.
Heal 1000 of health.
Complete all quests.
Spend 10000 gold.
Deal 5000 of magical damage.
Win 20 battles.
Deal 15000 of physical damage.
Put artifacts on the hero.
Deal 5000 of physical damage.
Lose 2000 of health.
Spend 200 of mana.
Win in 5 battles.
Complete Tutorial.
Summon 5 skeletons.
Resurrect after death.
Win in 5 battles in the mode of "Survival"