MTL - Tome of Blood - Chapter 10 -10-Resuscitated Cthulhu

After becoming #1 in the world after playing a grand strategy game as the most difficult faction on immortal level difficulty, MC receives an invitation to compete in an even more challenging game which takes the MC into the world of the game itself, but as it's weakest lord who will die two days later that appears only as a cutscene in the tutorial as first of many deaths to rock the continent until only one survives to proclaim a new eternal empire.Can the MC use his game knowledge to successfully survive his impending doom, and rise from the ashes to reclaim the glory he'd won before?

The world is terrorized by the powerful Black Witch who has been sealed in the moon. Every ten years, the night of Hexennacht arrives and a chosen witch must battle the Black Witch in hopes of finally defeating her.

As the current decade’s Hexennacht approaches, a mysterious girl named Kagami Kagami arrives and meets Horinouchi Mitsuru, the daughter of the previous Hexennacht representative.

It takes place between Kyoukai Senjou no Horizon and the City Series, two other series by the author.

The system asked: “What happened to the slag man?”
Bei Yu Tang answered: “Destroyed.”
The system asked again: “What happened to the boss?”
Bei Yu Tang immediately ran away!
Whether abuse of slag male or white lotus, she, Bei Yu Tang is very skilled.
But regarding abusing the boss, forget it!
Big BOSS’s fighting power is too strong, for small shrimp like her, it is still the best policy.
She did not want to destroy the boss, but was destroyed by the boss.
BOSS lord: “Wife, who do you want to destroy, let your husband do it.”
Bei Yu Tang excitedly replied: “System monarch.”
System: (face filled with tears and dead … …)
[Story of pampering, 1v1, Straightforward story, Easy and humorous]

- Description from 69shu translation

In a world where kingdoms rise and fall, a seasoned player unexpectedly finds himself transmigrated into the very game he once mastered—Caldera. However, his new life as a ruler comes with a crushing twist: severe debuffs and harsh restrictions on his talents make survival nearly impossible. Against overwhelming odds, he fights tooth and nail to carve out a legacy. Despite his brilliance in strategy and marvels in combat, failure becomes his ultimate fate.