Skeletons are the basic infantry of the Necropolis faction. Those troops are weak but they are numerous. Moreover their master can grow their ranks with the corpses of their deceased enemies…
Zombie (Upgrade: Plague Zombie)
Zombies are excellent defensive creatures. They are very hard to kill and even a small pack of them can sustain the charge of far superior troops. They are relatively slow though and make for poor attackers. However their large number can compensate that. On top of that Plague Zombies have the ability to drain the stamina of their enemies in combat, thus progressively reducing their fighting ability.
Ghost (Upgrade: Spectre)
Ghosts are fast, incorporeal creatures. They can inflict severe damages to their opponents, and on top of that they are more resistant to non-magical attacks. Spectres also have the ability to drain mana out of their enemy.
Vampire (Upgrade: Vampire Lord)
Vampires are fast and skilled warriors. Eternally young but gifted with hundreds of years of combat experience, they are thirsty for their enemies' vital energy. Their attacks are so powerful that their opponents will not even be able to strike back. Vampires will suck life out of them to restore their own.
Lich (Upgrade: Arch Lich)
Liches are undead wizards who used their knowledge and power to evade their mortal condition, but at a terrible cost. They have the ability to fire Death Clouds that will drain the life out of any living creature. This ability doesn't affect Undead creatures, so you can use them to shoot at mixed groups of troops (your own and enemy creatures) without the danger of harming your own. Arch Liches are superior liches who preserved their magical abilities to cast spells. They will use their power to weaken enemy troops.
Wight (Upgrade: Wraith)
Wights are doomed souls thirsty for revenge on all living creatures. Their weapons are fear and life drain. Their attacks will grasp the enemy's heart in cold fear, thus reducing their combat skill and strength. Wraiths have the ability to take the life of one enemy creature, no matter how strong it is, while the rest of the stack will loose all its magical abilities and protections.
Bone Dragon (Upgrade: Spectral Dragon)
Bone dragons are the strongest Necropolis creatures. Although weaker than “regular” living dragons, they are also cheaper to recruit due to their undead condition. They will fly into enemy ranks, causing many casualties to the creatures standing in their way. The Spectral Dragons live half in the immaterial world, in incorporeal state. All non-magical attacks against them are consequently more likely to miss.