Era: 600 A.D.
The Mystic War is the name of the conflict between humans and Mystics that spanned several years in the Middle Ages. The exact roots of the conflict are unknown, but are probably to be found in natural prejudices of difference. The humans most likely always looked upon the Mystics with disdain for their odd appearance and ability to use magic. These prejudices might not have led to war if it were not for Ozzie and later, Magus. Ozzie preached a doctrine of vile hatred against humans, despite the likelihood that humans left the Mystics alone (as the Medina continent could not be accessed through normal means in the middle ages). Magus served as their spiritual leader, as he was immortalized in song and stone as the protector of the Mystic peoples. Somehow or another, contentions arose and the opposing sides declared war on one another. The Mystic Army was the primary combative army on one side, while the Kingdom of Guardia (specifically, the Knights of the Square Table) stood as the sole defenders of the world on the other. The declaration was done before 590 A.D., and the resulting warfare primarily consisted of Mystic raids on the continent of Zenan. The Mystics, thanks to the Magic Cave, could easily storm across the continent and beat a hasty retreat should they be outnumbered. The Kingdom of Guardia was bolstered by the leadership of Cyrus, who, with his squire Glenn, led the Knights of the Square Table against the Mystics and performed other duties for the king. In 590 A.D., King Guardia XXI sent Cyrus on a mission to recover the Masamune, presumably for use against Magus. This operation backfired; Cyrus was slain and Glenn was turned into Frog. The Masamune was broken, and the war could continue unabated for another ten years.
During this interim period, a sleeper cell directed by the beast Yakra infiltrated the Guardia Cathedral with the plot of overthrowing the kingdom. Additionally, a monster known as Retinite was created and left in Fiona's Forest to ravage the area. The Mystic Army dug in at Magus's Lair, and continued to stage raids; one such attack carried out with the aim of reaching Guardia Castle resulted in the destruction of Zenan Bridge. The factions would remain in a perpetual stalemate until the bridge's repair; around this time, the sleeper cell in the Cathedral was successfully exposed after Yakra abducted Queen Leene. Frog played a role in her rescue, but otherwise lived in the Cursed Woods away from battle. When Zenan Bridge was repaired, the Mystics launched a full attack on the kingdom; at first, the king was injured and the offensive stopped to catch its breath. Soon, an attempt to cross Zenan Bridge was launched, and the Knights of the Square Table defended northern Zenan -- at the cost of casualties. Before the Mystics could step foot on the continent again, Magus summoned Lavos at his lair, effectively killing him in the process. This totally disrupted the Mystic war machine and dismantled the war effort, though hateful feelings toward humans would persist to modern times. When Crono changed history, he launched an attack of his own on Magus's Lair, slaughtering several top monsters of the army. This weakend the remaining prejudices in modern times; later, a similar attack on Ozzie's Fort would totally eradicate the negative remainders of the Mystic War.
The combat of the Mystic War is an interesting point, as the knights of Guardia had to fight against magic. It is probable that choke-points such as Zenan Bridge were primarily used for defense. The settlements of Porre and Dorino were thus lucky not to have been sacked, as during at least one period in the war, Zenan Bridge lay in ruins and the Kingdom of Guardia would have been unable to relieve a beseiged city on the main continent.