Reincarnated as a Skeleton: Starting as a Necromancer

[Necromancer + Skeleton Protagonist + Game-Like + No Female Lead + Summoning + Building a Territory + Farming] I woke up to find I’d become a lowly skeleton soldier buried in a wasteland of bones! Soul fire flickered in my hollow eye sockets, and my bony claws gripped a rusty shovel. Then, a System panel lit up in the dead silence: "Bury a hundred corpses to receive the legacy of a necromancer!" Other people transmigrate and make a name for themselves. Am I supposed to be a janitor in a Western fantasy world? It wasn’t until that bottle of green potion seeped into the bones of my underling, growing armor over his skeleton and turning his spine into a spear, that I realized... Every corpse in this wasteland is an armory waiting to be plundered! When I backstab the kobold lord, when a skeleton archer’s bone arrow pierces the skull of one of his own guards, when the Coffin of the Dead devours the wronged souls on the battlefield and turns them into an undead army... The stones beneath my corpse-burying shovel tremble, and a throne of white bones is forged amid a mountain of corpses and a sea of blood. But the blood-red warning that suddenly flashes across the System makes my spine go cold: "Subdue a mythical undead within thirty days, or your soul will be cast into the abyss forever!" Looking at the one empty slot left on my contract list, I clench the bloodstained lord’s insignia in my hand. This time, I’ll make the gods hear the thunder of bones rising again!