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 or buy coffee on Ko-fi.com

https://www.patreon.com/snowstar

https://ko-fi.com/snowstar5061

Weapon seller in the world of magic

The voice of a stranger from nowhere startled everyone. Even Xie Mei, who was prepared to break her vow and use the bow due to an emergency, got surprised by the new entry.

Soon, the demon materialized himself and appeared before the assassins.

"Who are you?" As they felt nothing from the demon king, they were more alert.

Bael smiled in response, "well, who am I is of no importance. What's important here is that you aren't here to assassinate the girl but to give answers."

"Kill him." The leader of the group codenamed Falcon, ordered the others. As they tightly gripped their daggers and were about to charge at their new target, Bael snapped his fingers and all of a sudden, large bones looking like tusks erupted from the ground and pierced each of them in their legs or thighs.

Capturing the assassins