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.
***
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.
**************
Author's current works: War Online, My Soul card is a Reaper
Author's other notable works:  The Last Slytherin, The Sharingan Hyuga
**************
You can also support the Author through Patreon

https://www.patreon.com/snowstar

Weapon seller in the world of magic

Year 18, Age of Mark;

Earth 43, Plane of Ice and Fire;

At the shores of a beautiful frozen lake in the wilderness, six teenagers were seen sitting together and having a chat or more like arguing with each other.

"No, it is too risky, Steve. You never operated it before," said a girl with pointy ears. She was frowning in displeasure.

"C'mon, it's not like we are some mortals that we needed to worry about such risks. We can even breathe in space," replied Steve. He added, "And it's not fair that only the eldest brother is allowed. We are not weaker than him in any way."

"Then, why don't you tell it to Dad and convince him?" The elven girl argued.

"If uncle knew about it, you will be grounded this time for sure and even your mom won't be able to save you," a male with pointy ears supported her. He was her twin.

Chronicles of Frozen Time: A Reckless Journey to Save the Past