Waves of Calamity (Web Novel)

The Waves of Calamity are mysterious phenominon that occur every so often in the world and warrent the summoning of the Four Saint Heroes, to confront. The events true nature, as well as its cause, are largely unknown. They occur on a monthly basis until the Four Heavenly Beasts appear for the final four waves, at which point it varies. The Four Saint Heroes and their companions can be summoned directly to the location of the occuring wave, except in the case of the Four Heavenly Beast's waves, Naofumi also found that adding a leader of another party, say a group of knights, as a member of your own party also transports him and his subordinates to the location of the wave as well, making it possible to transport a small army there(or presumably a whole army if one does something like add a highly ranked general as a party member.)

History
There have been numerous waves in the history of the world, enough to leave a lasting impression and legend behind. It is known that the Spirit Turtle, Houou, and Kirin were all sealed away during past waves rather than defeated, and that no hero has ever actually defeated the waves, rather they have all just managed to survive the waves instead, which is not possible during the Last Wave Period, as there will no longer be a way to seal the creatures away anymore.

Last Wave Period
The Wave period in which the Four Saint Heroes Naofumi, Motoyasu, Itsuki and Ren are summoned is noted to be the very last one, meaning that if the world is not saved here it will ultimately be destroyed.

First Wave
Struck at what would later become Rock Valley in Melromark, this Wave killed Eclair's father, both of Raphtalia's parents, and rendered several demi-humans homeless and/or at the mercy of slavers, this is not helped by the King of Melromark's hate of demi-humans and the queen's unfortunately timed absence. This event led to the king summoning the Four Saint Heroes.

Enemies
Cerberus(Boss)

Second Wave
Struck near a small town in Melromark. The casualties were severely reduced due to the quick response that the knights could provide due to the distance from the Castle Town being short, and the heroes Motoyasu, Itsuki and Ren managed to easily slay the Chimera acting as the boss. Meanwhile the Shield Hero Naofumi directly protected the nearby town and saved countless lives in the process, but would go unrewarded by Melromark's King for his contribution.

Enemies
Chimera(Boss)

Third Wave
The Third wave occured near a number of villages. During this wave Naofumi managed to bring several knights with him at the time of teleportation, which was good because the distance from Melromark's Castle Town meant it would take a day and a half for the knights to arrive normally. Together with the knights and some adventurers, as well as a certain old woman who happened to be a retired Lv.100 adventurer Naofumi managed to defend these towns. After three hours Naofumi was forced to investigate why the other three heroes hadn't stopped the wave yet by killing the boss, and finds them defeated by Glass, who herself had already killed the wave's boss. Naofumi engages and defeats Glass together with his party, forcing her to retreat while warning him not to believe the waves are just a natural disaster.

Enemies
Soul Eater(Boss)

Unseen foreign Waves
At least two waves(likely the 4th and 5th respectively) occured in foreign countries and required the intervention of the heroes Ren and Itsuki to come and resolve.

Seventh Wave
The 7th wave occurs when the heroes Motoyasu, Itsuki, Ren and their parties foolishly release the Spirit Turtle from its seal, effectively skipping any waves that should've occured prior to this one and pushing this one forward. The fourth hero, Naofumi, together with an allied force led by Melromark's Queen, confront the Spirit Turtle in a bid to seal it anew, but find that it is impossible to seal the beast. Naofumi interprets the messages of a previous hero, one named Keiji who helped seal the turtle to start with, that the turtle can only be killed by destroying both its head and heart at the same time, which he proceeds to do just as it started storming the Castle Town. This incident itself took roughly a full month to resolve.

This Wave caused a blue hourglass with the number "7" to appear in it, and showed that the new wave, the 8th, would occur in 3 months, not 1 as previously seen, allowing the heroes ample time to prepare. Naofumi himself starts up a small village in Rock Valley to raise soldiers for the next wave.

Enemies
Spirit Turtle(Boss)

Spirit Turtle Familiars

Eigth Wave
The Eigth Wave occurs 3 months after the 7th, and incurs the revival of Houou. The allied forces and Four Heroes mounted a massive force to confront Houou, who revives in the form of two Pheonix that must be simultaneously slain(should one go down before the other, it'll self destruct and both will revive from its ashes). The allied forces nearly defeated the two Houou without suffering heavy losses, but the sudden interuption of a certain individual killed one of the Houou too early and triggered the second to self-destruct, killing a large number of the allied force, including Atlas. Atlas' sacrifice allows Fohl to awaken the Seven Star Gauntlets and with her dying words she encourages Naofumi to unlock the Shield of Compassion, which allows him to vastly increase the power of all slaves, demi-humans and companions forming the allied force with sudden growth corrections. The allied forces swiftly slay both Houou with this newfound power and begin hunting down the one who interrupted and caused the deaths of so many of their comrades.

Enemies
Houou(x2)(Boss)

Houou Familiars

Ninth Wave
Occurs 3 days after the 8th wave in the kingdom of Folbley and comprises of Kirin's unsealing. This wave is resolved by Tact and his army soon after. Naofumi theorises that the reason this wave struck so fast is either due to the swiftness of Houou's supression preventing casualties, or Tact's senseless murdering of four seven Star Heroes sometime prior to the 8th wave.

The blue hourglass summoned by the Spirit Turtle dissapears after Kirin's demise and the tenth and last wave is depicted with a normal red hourglass, which shows that it will occur in 1 week.

Enemies
Kirin(Boss)

Tenth Wave
Will incur the summoning of Ouryuu. Naofumi assumes that the reason this event is depicted with a normal red hourglass unlike the previous three is because unlike them Ouryuu isn't sealed nor is his seal breaking. Gaelion assumes Ouryuu might be an assimilation of the Dragon Emperor Cores, perhaps implying that Ouryuu himself is the dragon emperor and he will revive from his cores.

Enemies
Ouryuu(Boss)

Trivia

 * The final four waves are spearheaded by the Four Sacred Beasts: the Spirit Turtle, Houou, Qilin and Ouryuu repectively.
 * It is indicated that the deaths of one or multiple heroes during the incursion of the Waves has dangerous consequences and must be avoided at all costs.