One of the things I enjoy the most in wow is Blizzard makes references to a ton of real life mythology in designing their characters, locations and lore.
Ethereal and Draenei:
Alien species that have extremely advanced technology that live among us just like Grey aliens and Reptilians.
The Nerubian, necropolis and ziggurats:
In Hollow Earth theory, it is said that both Antarctica and Arctic have entrances to the underworld where the subterranean “beings” just like the Nerubians live who also happen to have extremely advanced technology (a dyson sphere inside the Earth) that created the floating citadels - Necropolis. Both necropolis and ziggurats resemble the appearance of a pyramid. Some believe those similar looking “mountains” in Antarctica are in fact pyramids, which would mean there were civilisation in Antarctica before.
Elemental Lord Neptulon, the Naga and Azshara:
The elemental lord who controls all waters is a reference to Neptune/ Poseidon in roman and greek mythology. The Highborne of the Kaldorei Empire sank deep into the ocean 10,000 years ago during The Great Sundering much like Atlantis which was said to be either sunken into the depth or pushed by the Great Flood 12,000 years ago into today’s Northern Africa near Morocco and Mauritania where the Eye of the Sahara was found.
The Vrykul:
The Vrykul were created by the titans during the ordering of Azeroth. In the Bible, there’s a giant race called the Nephilim who were cruel and evil, they were the offspring of Angel (aliens?) and Human. In many ancient mythological, their first rulers were all giant-looking and had very long lifespans. In wow, the Curse of Flesh caused Vrykul slowly deformed into the human race which has a much shorter lifespan. On the Sumerian King List, it is stated the first dozens of kings ruled ridiculously long, some in tens of thousands of years before succession.
Giants are also a major component in scandinavian mythology. In the beginning of the universe, there were two elements, frost and fire just like the Light and Void in wow. The conflict between the two elements created a huge gap in the middle and also some poisonous “rivers”. Some of these water fell into the gap and merged with the fire and frost element in it and became the first living being in the universe, a giant named Ymir (attack of titan is also based on this mythology), who is Odin’s (In wow we have Odyn) great great grandfather.
The World Tree:
In scandinavian mythology, the world is described as a tree where 9 planes of existance (similar universe in wow) reside in different part of the tree. At the crown of the tree is Asgard, the realm of Aesir in wow is like the Halls of Valor (there’s even a rainbow bridge in it, which is the only mean to get to Asgard from the other 8 realms/ planes). Alfheim and Nidavellir are the realms of “light” elves and dwarfs. And Helheim is also called Helheim in wow, the realm of the dead.