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