As the years went by experimentations began to decline as each new ruler became less and adamant about the titan elixir. However, a new threat was on the rise. A neighbouring kingdom was on the attack.
The Kingdom of Eldia came into the light with shocking weapons. Just like Ulric LeBlanc, the kingdom of Eldia had people with the ability to shift into titan forms. However, the Eldian Empire only showed to have obtained nine transformations but the transformations did not kill the user after a short amount of time. This was thought to be the descendants of Ymir, those who had inherited the powers that she had once had.
Upon their first arrival, the king of Eldia met with the king Rhea. The two shared an agreement with one another. There was evidence from the Eldian King that there were ties between the two nations.
With this connections the King of Rhea made the agreement that they were allies with one another. He shared any information that was still kept about titan shifting properties and presented it to the Eldian King. The two nations then fought side by side together and forged a large Empire.
However, after many years, the once great nation of Marley had obtained seven out of the nine titans and thus began to over throw the Eldian Empire in what became known as the Great Titan War. Long ago it was believed that once one of the nine titans had perished under the Curse of Ymir, then a new born child will be granted with the power. However, the people of Eldia had developed a serum. It was a way for someone of Eldian blood to turn into a titan. Although, once the serum was injected they had turned into a mindless giant much like how Emil Weismann's elixir had turned people into giant mindless monsters. During this experimentation, it was discovered that the newly formed titans were attracted to humans just like in Emil's papers. However, the titans were in search of something and that something was the power of one of the nine. One of the nine who inherited the power did not use their powers fast enough and was consumed by the mindless creature. It was at this time that the creature had reverted back to their normal human state.
Further discovery suggested that the person in question who had consumed one of the nine had then in return gained the power and became one of the nine themselves. It was suggested that the nervous system of the body was the key component to this process as it was the main part that connected the body of a person to their titan form. However, it was not just the nervous system but the spinal fluid of one of the nine titans that was required to turn a mindless titan back to normal and inherit the power. A fluid also found the brain that would influence the will Ymir to waken the chosen power of the titan that they had consumed.
With this concept, Marley had taken hold of the research. They had taken several Eldians and therefore began to control seven out of the nine titan powers. Rhea refused to get themselves involved in the matter fearing that they would fall subject to the wrath of Marley.
King Fritz of Eldia, did not want to fight. He instead took his titan and his people to an island called Paradis. On this island he established a new kingdom and a new era. This left Marley full control over the land once more and established a great military strength against anyone who would oppose them.
Rhea cut their ties with Eldia when the great nation fell under and became silent. They established a connection to Marley allowing trade to occur between the two, showing that Rhea was no threat to them. This allowed Marley to become more advanced in technology with the help of Rhea.