Dragon Hourglass

It indicate the time & transport the heroes and their party to calamity region. Nothing other than was mentioned in the series.

Structure
It is a gigantic hourglass, approximately 7 meters tall, with red sand enshrined. It is decorated and gives off an indescribably divine aura.

Purpose
The Red Dragon Engraved Hourglass is  famed clock tower which indicate the time of occurrence of Wave calamity. When the final bit of sand from the hourglass drips down, it indicates that wave phenomena occurrence. The Heroes along with their merry band will be teleported to where the wave of great calamity will occur within hour glass's  territory range.

The hourglass is needed to perform a class-up. Almost all region whether it is a human inhabited or uninhabited regions, all have similar Dragon Engraved Hourglasses that can perform the same function. Mostly it is within the country's capital or capital built in the specified region. The country alone will specify who gets to class up and not anyone could. By using special items, one can modify the class advancement procedure like Fitoria gift of Ahoge to Filo which doubled all the status of Naofumi's party which was quiet rare.

The dragonhour glass can also reset the levels of individual back to Level 1. It is mostly used on criminals.

But the heroes must sync with said hourglass before they and their associates can be summoned to that country's wave. When registered, the heroes get the display of the time of the calamity. But doesn't predict the region where the calamity was going to hit.

By the end of the series all the Red Dragon hour Glass stopped instantly, indicating the heroes victory over the wave. It was then expected to be just only for class up.

Regions
It is inside Melromarc's Castle Town's huge in the town plaza in the middle of the church. It was also shown to be in the underwater submerged temple of Cal Mira Archipelago. It was also shown in the hidden country protected by Fitoria, Fitoria also mentions that there are numerous hour glass across the world and she manages the region where there is no human settlement.

Summary
Naofumi wasn't aware of how the system works. He was told about Red hour glass and went there. He got himself unknowingly registered to the Melromarc Hour glass, when he actually went to check for the time of the wave. Naofumi was under the impression that he will be teleported to the region any where in the world if the wave occurs. But it wasn't the case, as the Melromarc's hour glass transport heroes to the wave affected region with in its jurisdiction. The heroes must register to hour glass of the particular country to fight the waves. When he was framed of kidnapping Princess Melty, he was worried that even if he run to other country, he might be teleport back to Melromarc during the time of wave and might be arrested, not knowing that he could have easily unregistered by registering in other country's hour glass.

Trivia

 * Their origin was a mystery as all the records of it were destroyed or forgotten in course of time.