Necromancer? Death Mage!

Carl was reborn in a different world and became a black mist. What hurts him a little is that even if he doesn't do anything, it will gradually dissipate, and Karl's life has entered a countdown. Fortunately, after killing other creatures, he can harvest their souls and gain soul power. And soul power can continue his existence. [Harvest Goblin souls and gain 5 soul power] [Harvest kobold souls and gain 8 soul power] [Harvest the dragon soul and obtain...] "I'm telling you, we goblins should stay away from those humans." In a certain Goblin settlement, a Goblin chief stood on a stone and taught his people. "Because among those humans, there is a guy who always wears a black robe and is very scary. He kills monsters without blinking an eye. The other monsters call him the monster killing machine." The Goblin Chief spoke vividly, "That guy also likes to say one sentence, called..." "Three coppers for one soul, no buying and selling, no killing~" "Yes!" The Goblin Chief looked appreciatively at the tribesman who answered the question, only to see a figure wrapped in a black robe standing there. …