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 prophecy of the elves basically states that a summoned hero will save the world from the demons.

He will sacrifice himself to seal them up, but they will eventually escape as time passes.

A great evil from the banished dimension of the Void realm will be returned, spreading chaos all over the world.

In times of turmoil, another mortal visit the world and free them from slavery.

He holds the darkness in his heart but also controls divinity at the same time.

He vanquishes the demons and becomes a hero.

He takes the princess as his bride and protects the world as his own.

Finally, he brings the humans with him and establishes the harmony between the elves and the humans.

Upon witnessing the powerful divine energy blast from Mark, the High Priestess became confident that this second human from the prophecy was none other than Mark himself.

The High Priestess' request