Jaeanggeum Necromancer Euntoehaneun Beop

Enslaved by an archmage in another world for thirty years, Jihyeok is finally sent home to Earth with a pile of treasure. But when his riches disappear in transit, he’s left with nothing but his necromancy powers and a lazy attitude. Even worse, while he was away, Earth was invaded by monsters pouring out of gates. Posing as an Awakened, he summons armies of skeletons—not to hunt in the gates, but to start a business and earn his retirement funds with as little effort as possible!

(Source: Tapas)