“Sometimes you will never know the value of a moment until it becomes a memory.” – Dr. Seuss

“Isn’t it funny how day by day nothing changes, but when you look back everything is different?” – C.S. Lewis

If you are one of the rare people that hasn't seen this gem yet, I would highly recommend Overlord. It is currently on Crunchyroll.

Through the main character, this anime’s premise asks, “Have you ever nostalgically wished that a game you once loved was still in its heyday? Did you ever miss the friends you shared it with, at that point that they had not yet moved on with their lives?”

Thus, the opening is one many gamers can sympathize with. It can hold true for people who played Massive Multiplayer Roleplaying Games (MMORPGs).  It can hold true with those who remember the glory days of their Tabletop Roleplaying games (TTRPGs).

This can be especially powerful for the Dungeons Masters, Storytellers or Guild Leaders of such games.  The protagonist is a reflection of themselves.

Overlord pulls you into a cleverly packaged horror, fantasy Isekai story.  It is also a master class in world building.

The anime is significantly softer for a tv audience. The original light novels and manga were far more dark and graphic in their storytelling.

The story is centered on an online guild’s work with what is a player created dungeon that can be won or lost in Player versus Player (PVP) or Guild versus Guild (GVG) combat. The winning guild gets to rebuild the dungeon how they wish and redesign the non-player character non player characters or monsters to their desires.

In this case, it was a guild of horror fans that created a vast amount of deeply creative monsters, who were highly geared towards destroying enemy players. The original idea was for the guild to wear down their enemies and have a dramatic final pvp battle at the bottom of the player dungeon / player city / player home(s).

The final battle the guild dreamed of never came, as the various guilds they fought never survived the first few floors. The years rolled on and the guild slowly fell apart due to real life commitments and complications.

This highly complex player driven project takes place in an online world that is at least as complex as first version of Star Wars Galaxies (SWG). Its last player is the guild leader, who was alone keeping the lights on for at least a year, waiting for his friends to return.

He waits as the servers shut down and this world he had sank so many thousands of hours into will be destroyed. For a brief few minutes, he does so with guildmate who also briefly visits for a few minutes and leaves.

Once again alone, the guild leader sits there in the memory of his guild’s glory days. The server counter hits its shut down time.

The game goes offline. The player created pvp horror dungeon becomes real in another world.   

The player now inhabits the body of his undead character.  The NPC monsters come fully alive and they are fully sentient.   Thus, the real story begins…

https://en.wikipedia.org/wiki/Overlord_(novel_series)

To quote wiki, 

In 2126, a Full-Dive Massively multiplayer online role-playing game or DMMORPG called YGGDRASIL was released, standing out among all other DMMORPGs due to its unusually high ability for the player to interact with the game. After an intense twelve-year run, the game servers are about to be shut down. Within the game exists a guild, Ainz Ooal Gown, once consisting of 41 members and credited as one of the strongest guilds in the game. Now only four of the members remain, the other 37 having quit the game, and only one, a skeletal Lich "Overlord" character named Momonga, continues to play as the guild leader, maintaining their headquarters in The Great Tomb of Nazarick. In the minutes before the shutdown he invites the remaining guild members, but of those only one appears and only for a short while before leaving. While saddened by this, he accepts the reality that his friends have their other lives to take care of and decides to stay logged in until the servers shut down.

When the shut-down time arrives, Momonga discovers that the game hasn't vanished; instead, it appears as if Nazarick has been transported to another world altogether and its various NPCs becoming actual living beings. Momonga has been trapped in the form of his game avatar, leaving him unable to use the normal player functions such as General Message, or even log out. With no other option, Momonga sets out to learn if any players like himself are in this new world. Taking on the name of the guild, Ainz Ooal Gown, as a message to any other remaining players, Momonga begins exploring the world in an attempt to figure out what has happened while searching for anyone or anything that could help him solve this mystery, while ensuring the safety of Nazarick. Ainz Ooal Gown seems to have modifications made to his behavior by in-game mechanics, because he demonstrates no moral qualms with killing and other actions that are taboo in the real world. This is a story about the psychology of a creature with near-limitless power who is beyond ethical concerns.

/salute