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