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

Silence filled the carriage traveling at the front as Qin Yu became completely honest with Mark, who left Song Yue and joined the other one.

The crown prince expected to get snubbed by Mark after revealing his current situation, but instead, he saw the weapon seller break into a peal of laughter and commented, "It is perfect, Prince Yu. It made my job a lot easier."

Qin Yu misunderstood that he was being mocked by him too and felt a bit angry. However, in the next moment, his eyes widened as Mark continued to say, "How about I solve your problems? There's a simple solution."

"Eh? What do you mean?" Qin Yu wondered whether Mark was suggesting the assassination of the fourth prince and he planned to reject the idea as he was against such a thing. Not to mention, the repercussions in case the plan will fail. Thankfully, he didn't voice it out and his patience rewarded him quite well.

Plan to create a puppet emperor