MTL - On the Wedding Night, Ms. Cui Realized - Chapter 38 nightmare

Sue Kirin was a loser. Thirty years old with no hope for advancement at his job and no redeeming features except one, Magic. For as long as he could remember Kirin had dedicated his life to practicing the Arcane. Unfortunately, when he was passing down his knowledge to his niece, she lost control of her power resulting in a backlash of vicious energy that resulted in her being sent to the hospital, her life in critical danger.

One day, Zhang Fan, a poor medical student, receives a medical system from the future. This turns him into a new shining star in the medical field. Along the way, he must face medical corruption, competition, and infighting from other doctors, and even find time for a love life as he strives for the top of the medical field!

- Description from Novelupdates

Just like how everyone adored heroes in their childhood, a certain young man adored those powers hidden in shadows. After hiding his strength and living the mediocre life of a mob character by day while undergoing frenzied training by night, he finally reincarnates into a different world and gains ultimate power. The young man who is only playing at being a power in the shadows, his misunderstanding subordinates, and a giant organization in the shadows that gets trampled…. This is the story of a young boy who had adored powers in shadows possibly eventually reigning over the world of shadows in another world.

Ajax was an orphan who survives a massacre along with his friends but unfortunately gets separated from them.

Fortunately, after a turn of events, he successfully gains a system which helps him increase his cultivation, but doesn't know what it is called.

But he knows one thing for sure, this system is very powerful and helpful in taking his revenge.

“Whoever you are, I am gonna find you”, Ajax mumbled himself with a disgruntled expression.

In a world where Summoning of an elemental spirit is done through a dream when they are 15 years old, Ajax with the help of a system and his summoned spirits sets out on a journey to seek revenge against the mastermind behind the massacre.