In WoW Classic there is the instance Gnomeregan and the dungeon is designed for 5 players. The level range of the instance is 24-34 and the minimum level is 19. Gnomeregan is located in Dun Morogh, which is in the Eastern Kingdoms. It is the capital of the gnomes and it is a dream of gnome inventors, it is a city like it has never been seen before in Azeroth.
If you want to go to Gnomeregan, it doesn't matter which faction you belong to, because for both it's a relatively easy way. As an Alliance player, you must leave the Ironforge at the main gate and follow the path westwards. As a Horde player, the path seems to be further than it actually is. You can complete a quest and teleport to the instance.
Gnomeregan is an underground city and a technical masterpiece. Between the peaks of Dun Morogh, the ruins bear witness to the proud past of Gnome and Gnomeregan. When the Burning Legion invaded Azeroth, the Gnomes had to fight their own war. The Troggs came out of their prison, where they were imprisoned by the old gods. The mutated Troggs have now reached the city of Gnomeregan. The gnomes couldn't ask their allies for help, because the alliance itself was busy surviving. High Tinker Mekkatorque had thought of a strategy how to defeat the Troggs and wanted to kill them with the radioactive waste or flee. However, this didn't work and the Troggs mutated further and were now radioactive. Thus Gnomeregan disintegrated and many gnomes fled or became victims of the Troggs.
The bosses in Gnomeregan are: Liquefied deposit, Grubbis, Electrocutioner 6000, Crowd Pummeler 9-60, Dark Iron Ambassador (rare), Mekgineer Thermaplugg.
The first boss in the dungeon is the Liquefied Deposit. It is a contaminated water elementary and lives in Gnomeregan. It has been held in the groundwater of the gnomes and without a chance it has been spoiled and nothing is left of its pure form.
Grubbis is a trough and boss in Gnomeregan. Actually, the gas in the city was supposed to cause the Troggs to flee or die, but in Grubbis it has caused unexpected side effects. It grew in size and is now one of the most dangerous Troggs in Gnomeregan, patrioled by the corridors.
The Electrocutioner 6000 is a mechanopanzer and boss in Gnomeregan. This construct is the first attempt to use electricity as a weapon. The inventor Mekgineer Thermaplugg is much too impatient to test his inventions properly, so they are immediately tested in practice and he continues with a new project.
The Crowd Pummeler 9-60 is an invention of the robot engineer Glotz Wirdrikus. In the instance of Gnomeregan he is a boss. The construct belongs to the type Alarm Bot. Thermaplugg stole this successful invention to make a huge version of it. He released it and this had terrible consequences. Because of this, the council banned the innocent Widrikus.
The Mekgineer Thermaplugg was once the highest advisor to High Tinker Mekkatorque. However, this was not enough for him, he wanted to become High Tinker himself. Once he stood for election as a high tinkerer, but he was not taken because he was too ambitious. Thermaplugg wanted more than that, he wanted to be the first gnome king. Sicco Thermaplugg is a traitor and has appointed himself king of the gnomes. There are rumours that he knew about the attack of the Troggs and was even partly responsible. He betrayed the whole gnome people only because of wealth and power.