MTL - To Four Thousand Years Later - v5 Chapter 56 key and lock

I was reincarnated into another world, and I’ve brought the Horadric Cube from Diablo II with me.
Being a knight is cool and all, but being a wizard is pretty neat as well.
So, which one will it be?

- Description from Novelupdates

Tian Long, an orphan without much of a life in both his thirty year long life and lifespan!
To him, a single opportunity was displayed to transmigrate into another world with his Death Book!
"What's this? Is this the body of a three year old? Davis? Is this my name from now on?"
Finding himself possessing a small child, he becomes inwardly conflicted before he faces the truth and his reality!
Young Davis finds himself as the legal heir, the Crown Prince of the Loret Empire in the Grand Sea Continent, becoming a powerful cultivator in a short time...
However, is that all?
Follow his journey as Young Davis becomes a full fledged death's advocate while embodying into the Divine Emperor of Death in the world of cultivation!
"Mn? The route to become the Emperor is a given? Nah, I still don't want it..."
"Oh? I'm courting death you say? Unfortunately for you, death is already my woman..."

“There are no heroes. In life, the monsters win.”

...

In 2106, [Mayhem Online], a fully immersive VRMMO game, was released. Soon, it dominated the world's economy when people could exchange the in-game currency with real-life currency and vice versa.

In the year 2107, Flynn Grey, a 22-year-old college dropout with an ambiguous history, joined in the fray of billions of people that had already started playing [Mayhem]. Hoping to uncover the game's secret and earn a fortune, he spent months on adventures without fruitful results.

For better or worse, Shura, Flynn's in-game character, ends up in a great Wyvern's den, acquiring a hidden class and a monstrous race. Join him as he defeats his past and paves his way into becoming a true legend in both worlds.

Baek Ain is your typical lazy guy.

He graduated from university at age 22 with a random degree he chose out of boredom and stayed single because fate decided so until that event happened.

“What? Where Am I??”

After a horrible incident, Ain transmigrated to another world. Or precisely to be a villainous and mobs character.

He died countless times because of the world's protagonists, gathering hatred toward them.

“What the fuck! What do you mean I stole your wife? I've been single since coming into this world!!”

“Hero, please save this world.” A goddess is begging me to save her world from the Demon Lord.

“Wait... Begone thot! That Demon King is my younger sister from 69th Transmigration.”

“How dare you!”

A beautiful heroine is hugging me from behind, wishing to accept her feelings.

“Shoo, Heroine! I don't need useless baggage with me. Side characters are better than you!”

And so, Ain's journey began to end this shitty transmigration cycle.