Death March kara Hajimaru Isekai Kyusoukyoku (WN) - Book 15 - 15-25. Dungeon's Function

During this chaotic era, the darkness engulfs all.
In a struggle of fire and death, despair shrouds the continent.
The line between fantasy and reality becomes blurred as a speckle of starlight penetrates the night sky.
But is it enough to reverse the downfall and fate? To regain the lost glory?

Rhode is a famed player in the game “Dragon Soul Continent”. There, he leads the strongest player guild in the game, the Starlight Guild. Just as he defeats the last BOSS, the Void Dragon, he unexpectedly awoke in a world identical to the game.

As the Summoner Swordsman returns to the continent, waves will be cast in the rivers of fate. Can he face the coming chaos and avert the destruction of the continent?

As the future High-Ranking among Elven, I was meant to be dignified and holy—but my friends never gave me the chance. One is a human prodigy turned “cripple” after an accident, determined to prove everyone wrong. Another is the Demon King, whose idea of preparing for war involves turning his entire race into farmers. As I watch my friends stir chaos in their own ways, I can’t help but wonder—how did I end up in the middle of all this?

Crossing into the world of Naruto, and acquiring the One Piece system, with all the powers of the world of One Piece, swordsmanship, devil fruit, domineering.

-Do you think that your fire is very powerful? I have the burning fruit.

-Do you think that your thunder is very powerful? I have a thundering fruit.

-Do you think that your otter is very powerful? I have the frozen fruit.

-Did you said you want to die? Don’t worry, I also have a nickname: Death Doctor.

- Description from Novelupdates

“Kill them all - every last member of House Grim must die tonight!”That was the last thing Renard heard before his world turned to ash. One night was all it took for him to lose everything - his family slaughtered, his home burned to ashes, all because the other Great Houses branded them traitors.They thought they wiped a noble line. Instead, they created a monster.Rising from the despair of losing everything, Renard became the beast Sovereign. He embraced the darkness and rose to the position of the 7th commander of the dreaded demon army.Leading an army of Demons and monsters, he brought three legendary Heroes to their knees and crushed four Great Houses to dust. But just as revenge was within his grasp, the champion of Humanity - Klean Weaver's holy sword pierced his heart.Renard thought that was the end.But something impossible happened.He woke up in the past, in a time when his family still lived and House Grim stood strong among the Eight Great HousesA second chance!A chance to change everything.That wasn’t all.For unknown reasons, he inherited the Legacy of the Devourer, a power that lets him consume the strength of his enemies.Was it a curse? Or a blessing? He didn’t know. But for Renard, it is simply a tool to protect what's his.The Lords of the Great Houses think they're untouchable in their high castles. They have no idea what's coming.This time, the Beast of House Grim hunts first!!