To get this achievement you need to play as Necromancer Leader.
First you need to research Animate Ruins strategic spell. It should be quick as it is Tier I strategic spell. When you finally research it then you need to raze a city to the ground. The best way for it is to find a independent outpost, declare war on it and when you finally capture the city pick a option to destroy it. After few turns the city will be destroyed, then pick the spell from your spellbook and cast it on the ruins.