Skyrim: A Sorcerer's Tale - Chapter 20 - IX: Restoration and the Lizard Wizard

An angel made a mistake, resulting in Shiihara Daiki’s death. In order to hide the mistake, he was then sent to a different world. The angel will grant him one wish as a payment for keeping it a secret. Daiki asked for a Heavenly Castle floating in the sky without hesitation.

Suddenly a floating castle appeared in the new world, which causes confusion amongst the people. They attempt to contact Daiki in various ways. A country tries to steal it by force, while another seeks to befriend him. What in the world would Daiki do?

She, a 21st century mercenary queen, had crossed over into a tragically betrayed body of a waste. Waste? She will show them what it means to be a waste! Betrayed? With the Ancient Manual in her hands, she will astonish all the despicable men and cheap women!

Wait! Didn’t everyone say that she was an evil woman which everyone feared? Why is his Third Highness, full of mystery and charisma, so interested in her?

- Description from Novelupdates

Following a brutal and tortured death, a former assassin, known only by his codename Kuro, is given the opportunity to reincarnate in another world, a world with magic and monsters. Armed with an unrivaled healing factor and an inhumane pain threshold, Kuro opts to go for a reckless direct approach in this world instead of a stealthy and cautious one, and as a result, slowly gains attention bit by bit.

Having previously been a loner in his old life, he interacts and befriends people for the first time in his existence, however, his blunt nature also sees him making just as many enemies, both big and small. By combining his old assassin skills with the magic powers of this world, along with his high resistance to pain and rapid regeneration, he doesn't take long to establish himself as a formidable force in this world.

Initially, Kuro only faces minor threats, like weaker monsters and bandits. But before too long, the threats slowly but surely become more and more severe…from Zombies to a bloodthirsty empire to Vampires and Demons, and even divine beings…however, as the enemies he faces grow stronger, so does Kuro, gaining rare powers that have never or rarely ever been seen in this world…

In the Abyss, all beings are imprisoned, struggling bitterly to survive. One day, in the eternally dark lower world, a young boy has a chance encounter and catches a glimpse of the upper worlds. He is fortunate to witness wonders beyond even the most beautiful dreams. Realizing there are worlds beyond his own, he refuses to settle for mediocrity and vows to ascend to the top step by step.