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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Weapon seller in the world of magic

"Oh! Shit. Prince Wei's suspicion is true?" The Grand Secretariat was taken aback and so were the others. Panic struck a few ministers as they heard of the existence of a supreme realm expert.

Song clan's current head spoke in a hurry, "We have to send Ancestor Song Tai to deal with them. Does anyone have any instant means of communication with him?"

As everyone shook his head, Lin Wuying spoke, "Or we can take Lu Zhen's help."

"Are you serious, Lin Wuying?" Nie Rougang flared up when Lin Xue's father suggested the name. As a person who was on the side of the Crown Prince and Ji clan, he took the opportunity to put allegations against Mark.

"Lu Zhen kidnapped Ji clan's heir and handed him to the Kunyu bandits to take revenge.

He stole Song Yue away from Ji Mingyu when he was supposed to wed her.

He sold those weapons to Kunyu bandits who were using them to murder our civilians.

A letter to Emperor Shang