Snowstar

Mark is a genius military weapon designer who was kidnapped by a mafia gang after refusing to work for them.
They forced him to design unique weapons for five years, until one day he successfully escaped only to get shot by his trusted comrades.
*Ding! You awakened a weapon system.
When he opened his eyes, he was in a different body and in a different world.
"You want to kill a wild boar without being detected? Forget about bow and arrow. Here, I present you this sniper rifle."
"You want to kill a horde of goblins from the sky? Forget about those flying carpets and brooms. Here, I present you the fighter jet." 
"You want to kill a dragon? Forget about taking the help of the S-class adventure team. Here, I present you a nuclear bomb."
Join Mark Spencer/ Lu Zhen as he brings the whole world to its knees with the help of his weapon system.
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Note: Author isn't born in an English-speaking nation and has no editor either. So, please be understanding if there are any grammatical errors.
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Author's current works: War Online, My Soul card is a Reaper
Author's other notable works:  The Last Slytherin, The Sharingan Hyuga
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You can also support the Author through Patreon

https://www.patreon.com/snowstar

Weapon seller in the world of magic

A few hours later;

In the capital city of Lunaris, at midnight when people were supposed to sleep, thousands were gathered at the Palace Grounds as the King was about to make an important announcement.

Everything went as the princess wanted it to be. After informing the ministers, Shen Qiu made an announcement of the King's return to the public, handing over the crown in front of everyone.

Just like with the ministers, the people went into disbelief for a while. Shen Niu then took the charge and explained to everyone the story cooked up by the Princess.

According to his version, a decade ago, during the time of the rebellion by the former Supreme General Xuan Yi, the King was poisoned by a servant who was actually a spy of the leader of the rebellion.

Submarine or Destroyer