My legendary class is Husband Of Deathwill Sisters?! - Chapter 2

A mysterious natural phenomenon caused the Earth to be plunged into darkness. The world turned into an endless bloody chaos and mankind is on the brink of extinction…

"Locke transmigrated into an era where everyone had Battle Beasts. Daemons were rampant and humans were forced to build walls around their dwellings while depending on Beastmasters to keep those monsters at bay.

Transmigrated into the novel you read and became the heir of the Duke, only to be trampled under the protagonist's foot?Passerby villain?Appeared in only one chapter?“Who are you looking down on?”Ian cursed his destiny and vowed to change everything.[Ding!][A new quest has been activated.]'Oh? Do I have a system? Even better.'[Basic Quest 1: Don't let your flower slip through your fingers.]'Nice, I won't let go of her anyway.'...[Basic Destiny Quest 1: Can You Finish What You Have Started?]'Bring it on!'...[Ding!][You are at an important fork in your fate.][Unique Destiny Quest: Fight with all you have.]'Heh? Who are you looking down on?'As Ian completed one quest after another, he also inadvertently began to fall into a vortex of the unknown. He discovered there was more to this world than described in the novel.'Damn it! These suspense and twists, one after another, are killing me!'---Tags: Smut, 18+, Harem, no incest, weak to strong, Romance, Wizard, Magic, Knight, System, Multiple Planes, Elf, Demons, Monsters

…but it seems pretty doable.