Wraith/1.03

Wraiths are basic infantry units.

Dark Dwarves
The Wraith is a floating Undead unit with a very special ability to leech the EXP out of any unit it kills (this includes Lair Bosses and Heroes). Wraiths have a resistance to elemental attacks but are vulnerable to all physical. Like all Undead, the Wraith gets a natural combat bonus at night. Wraiths can be summoned instantly by the Ancestral Hall building, but at a greatly increased cost. They can also be upgraded by the aforementioned building. The Ancestral Spirit reseach allows them to be summoned instantly by Summon Spirit at the Ancestral Hall.

Benefits from Weaponsmith, Armorer, Mithril, and Forgotten Power researches.

Undead
This floating, ice damage dealing creature is the other upgrade possible from the skeleton and would be nearly useless if not for one very interesting ability: if it slays an enemy, it leeches all its experience! Yes, that includes Heroes. So use an army of these (costs some crystal) and hunt down the enemy Hero, and you have an instant level 20 juggernaut at your command! Can be upgraded to the stronger and faster ghost. The biggest drawback of the wraith is its vulnerability to physical attacks, at a time in the game when most attacks are physical. So be careful with them. Luckily, they can outrun most enemies when upgraded with the Haunting skill.

Benefits from Weaponsmith, Dark Mithril, Tombguard, Haunting, and Wailing researches.

Quotes

 * Ready: "Free, at last!"
 * Select: "Yes, Lord?" "What now?" "Feel my power."
 * Order: "With ease." "For You, my Lord." "My touch is death."
 * Deathblow: "Come to me!"