Arya remembered her history well and knew exactly how the war started between the Rhoynar and the Valyrian Freehold.

The war started because of a giant, sacred turtle.

One of the dragonlords from Volon Therys had butchered an Old Man of the River in the Rhoynar city of Sar Mell, which sparked the first of the Rhoynish Wars that would span for two and half centuries.

Princess Nymeria may not be born yet during that time, but she was born at a later date when it neared the Second Spice War.

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Princess Nymeria of Ny Sar was an infant when Bran used his greenseer abilities to bring Arya to the past.

"The child's mind is not as strong as that of an adult." Bran had said when he guided her into warging into the infant. "If you warg into her at a young age, you will be able to overcome the other consciousness, Nymeria's, and become her. Kill the child and let the woman be born."

And Arya had not hesitated and smothered Nymeria's consciousness in able for her to possess the babe's body.

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Being a Princess of the Rhoyne was so much different than being the Highborn Lady in Westeros. Arya soon found. As she grew older into the role as Princess Nymeria of the Rhoyne, the first born and heir to Ny Sar, Arya was able to do anything she wished, whether it be training for combat, or studying politics and war strategies alongside other Rhoynar Princes and Princesses.

Men and women ruled equally in the Rhoyne, which Arya felt liberating. It made Arya more determine to rule fairly over Ny Sar when it was time for her to do so. So she studied as much as she could about everything she needed to learn in regards to any matter of state.

However, it didn't necessarily mean that she was not going to put her other 'skills' to good use; the knowledge she learnt from the Faceless Men since Arya intend to share her knowledge to those who could be trusted. She wanted to create a guild of assassins when the time came to end the Valyrian Freehold. For Arya finally understood how the Valyrian Freehold had perished. She realized that it was mainly due to the assassination of the Fire mages who controlled the Fourteen Flames that resulted to the cataclysm.

Arya could start changing history by having her guild of assassins secretly teach the slaves in the mines of Valyria and start a rebellion from within. It would certainly end the Freehold's attempt to control the world and enslave more people.

Perhaps the Doom of Valyria may have even resulted from Arya's interference. And if it was the case, Arya did not feel guilty at all for ending a powerful and greedy civilization.