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