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

In the factory, the robotic Cerberus (Alina) was seen lying on the floor and sleeping.

Alina opened her eyes at once as she sensed her master's presence.

"Big Brother…" She greeted him by jumping onto him like a real puppy. Mark hurriedly dodged and scolded her, "Hey, do you want to crush me or something?"

"Oops!" Alina apologized, although her tone suggested that she was trying to act silly, not a heartfelt one.

"Forget it. Follow me." Mark didn't care about it and just walked to the table while Alina followed him from behind. He smiled as he looked at the parts spread all over the long table, "let's finish this up…"

They have what seemed like a 2-story building-sized missile, which is currently incomplete. "Now, for the warhead…"

Unleashing Song: The Birth of a Formidable Missile