Sumer
It was believed that when people died, they would be confined to a gloomy world of Ereshkigal, whose realm was guarded by gateways with various monsters designed to prevent people entering or leaving. The dead were buried outside the city walls in graveyards where a small mound covered the corpse, along with offerings to monsters and a small amount of food. Those who could afford it sought burial at Dilmun. Human sacrifice was found in the death pits at the Ur royal cemetery where Queen Puabi was accompanied in death by her servants. It is also said that the Sumerians invented the first oboe-like instrument, and used them at royal funerals.

Q: What realm was guarded by gateways containing various monsters?
Ereshkigal