ShadenSword

In a world where intelligent species are as many as starts observable in the night.There exists Guardians of humanity, The Wardens. The wardens were the protectors of the human clans and they were known as heroes. 

Heroes of what you might ask?,Well in this world of chaos,there was no race who were safe.Not humans,not dragons,not goblins.No race was safe from each other.Each race were at war at each other,either for resources or power,nothing was left.Everything was an excuse for war.This was the rise of the wardens.The wardens or otherwise the protectors of humanity would destroy any race who would try to extinct the humans and they had powerful and awful ways of doing it. Just as time went on passing,Humanity lived in peace and so did the Wardens.

However This peace among wardens wasn't lived on forever, Shadow the warden of shadows was  not the same as the other wardens, no he was different. He wanted to destroy the human race and rule the races.So he did what he had to. Over the years of fighting with the oher races, he kept their shadows and wanted to release them for his conquest. 

His time had reached and he had released the shadows he extracted from killing the most powerful beasts. Suddenly the wardens were up against millions of creatures all alone, all millions of shadows fighting for the Emperor of Shadows. The Warden, Shadows. 

Although much was sacrificed the wardens won, but the losses overweighed the gains as almost 99 percent of wardens were gone and died along he war, only leaving 5 wardens. 
WARDEN OF FLAMES
WARDEN OF WAVES
WARDEN OF CRYSTALS
WARDEN OF THUNDER
WARDEN OF WINDS

However the 5 wardens were totally worn out, so inorder to revive their power back they had to go to slumber for 100 years. Humanity knew that they're hopes were gone however they couldn't hold the inevitable thus they built the citadels to honor the 5 wardens and let them sleep. 

The wardens made their promise to return and help humanity but finally after 100 years, Ashfall the warden of Flames is shocked as he wakes up to a peaceful era where all the races of the globe live harmoniously among each other. 

What will Ashfall do in a world that he is forgotten. A world where he has no purpose. Will he finally rest peacefully.

–––
Yes, use of mana Is present in this world. So is spells, magic and also all kinds of races are present, from dragons to goblins to you name it.. 
Also it follows slice of life theme. 
Any other questions will be answered in the comment section under author's review.

Table of Flame Bound Warden

Table of contents

Volume 1