Rydia was born to one of the few remaining pure-blood Summoner families in Mist. Her mother was known as the protector of Mist, and she used the Eidolon Mist Dragon to protect her village, isolated from the outside world but for the Mist Cave. 

However, one day, the Dark Knight Cecil Harvey and his best friend, Kain Highwind, were ordered by the King of Baron to deliver a ring to the Mist Village and slaying the Mist Dragon. 

As a rule, whenever a Eidolon dies, the Summoner who Summoned it dies as well. As a result, Rydia's mother died. Cecil and Kain came to Mist afterwards, and the ring releases Bombs all over the village, setting it on fire. Cecil and Kain found out the bad news about Rydia's mother from her, and offered to take her to safety. 

However, Rydia overheard that Cecil and Kain killed the Mist Dragon, and would not accept help. Instead, she summoned Titan to cause a massive earthquake which caused a landslide in the eastern mountains, separating Cecil from Kain.

Rydia was wounded in the earthquake, and Cecil took her to the desert oasis of Kaipo to let her rest. Cecil tried to ask her for her name, but Rydia refused to speak to him. 

That night, soldiers from Baron came to Kaipo in search of Cecil, and Cecil learns that the King of Baron wanted all Summoners eliminated, saying that they were too dangerous to be left alive. 

Cecil fought off the soldiers because he was already questioning the King, and he did not want to cause anymore trouble. Rydia acknowledged Cecil's sincerity, and told him her name.

The next day, the two discover Cecil's childhood friend Rosa Farrell was in Kaipo stricken with fever. 

The doctor said they had to search for the Sand Pearl in order to cure her. Rydia and Cecil went north through the Underground Waterway to Damcyan, and met an old man, Tellah, on the way. 

However, the three arrived at Damcyan just in time to see the Red Wings attack and steal the Crystal of Fire. At the top of the castle, they found Anna, Tellah's daughter, wounded. 

Tellah blamed it on Edward von Muir, the prince of the kingdom, and the two got into a fight which Anna broke up. Anna died, and Tellah departed, swearing vengeance on the new commander of the Red Wings, Golbez. 

After Anna died, Edward began to cry, but Rydia and Cecil had to snap him out of it. Edward then agreed to take them to the Antlion's Den, where the Sand Pearl was. The two retrieved the pearl from the Antlion and cured Rosa.

Recovered, Rosa decided that they needed to defend the remaining Crystals, and that the Crystal of Air in Fabul was the next target. 

However, they had to cross Mt. Hobs, a mountain blocked by a thick sheet of ice, in order to reach Fabul. Rydia was the only one who could melt the ice by casting the Fire spell, however, she claimed she could not cast the spell. 

This confused Rosa, as Fire is one of the most basic black magic spells there is. At Mt. Hobs, Rydia revealed her hatred of fire and refused to cast the spell, as fire had destroyed her village. 

With the encouragement of the group, Rydia overcame her fear and cast Fire, and the group was able to save the Monk Yang Fang Leiden on the mountain from Golbez's monsters.

In Fabul, Yang warned the king of Baron's incoming attack, and Cecil and Edward helped defend the castle while Rosa and Rydia were put on relief.

 However, after the fight against the Baronian army, Cecil was cornered by Kain, who had now turned against Cecil, in the Crystal room. The two dueled, and Cecil lost. 

Golbez then defeated Edward and Yang, and took Rosa as hostage. Kain took the Crystal and left. Rydia then cured the party. 

Cecil decided their best course of action would be to sneak into Baron by sea and get an airship from Cid Pollendina, who was also skeptical of what Baron was up to these days.

The party boarded a ship provided by the king of Fabul and set sail towards Baron. 

However, on the way, the ship was attacked by Leviathan, the Lord of All Waters. Rydia was blown off the ship, and Yang dove in to save her. 
The attack scattered the four, and the fates of Edward, Yang and Rydia were unknown. When Cecil reunites with Yang, Yang says Rydia was swallowed by Leviathan, and the group assumes she perished.

In reality, Leviathan took Rydia to the Feymarch, the home of all Eidolons. 

Time moves faster in the Feymarch, so while Cecil and his allies were separated from Rydia for only a short period of time, years went past in the Feymarch, and Rydia grew into a young woman at an accelerated rate. 

She honed her skills as a summoner and developed her powers with black magic, although she lost the ability to perform white magic. 

The queen of the Feymarch, Asura, told Rydia about the danger Golbez was placing the world in, and eventually Rydia decided to leave the Feymarch and return to Cecil to help him.

Cecil and his allies had entered the underground world where the Dark Crystals lay, and were attempting to protect the Crystal in the Dwarven Castle from Golbez. 

Golbez summons a Shadow Dragon which instantly kills all party members except Cecil. 

However, Rydia arrives and summons the Mist Dragon to defeat the Shadow Dragon, and rejoins the party in battle. Golbez is defeated, but he has enough strength to steal the dwarves' Crystal by teleporting away after his remaining hand grabs it. 

Rydia explains to Cecil and his allies about what happened to her, and rejoins them as they attack the Tower of Babil in order to get the other Crystals back.

When the attack on the tower fails, the group returns to the surface and enters a hidden passage to the upper levels of the tower through the Eblan Cave. 

At the entrance to the tower, they find one of Golbez's Archfiends, Rubicante, battling the Eblan prince Edge. 

Rubicante badly wounds Edge and retreats, and the group proposes they work together to defeat him. 

Although Edge initially rejects the idea, his injuries prompt Rydia to cry, as Yang and Cid seemingly died before they returned to the surface. Edge says he can't stand to see a pretty girl cry, and after Rosa heals him, he joins the group.

Atop the tower, the group battles Edge's mutated parents, and eventually dispatch Rubicante. 

The party enters the Crystal Room, where they fall into a booby trap and fall to the Underground and find a new airship: the Falcon. 

With the help of Cid, who survived his supposed demise, the airship is remodeled to fly over magma and reach the cave where the final Crystal lies. 

The group then enters the Feymarch and battle Asura and Leviathan to gain their help as summons for Rydia.

The party heads for the Sealed Cave and open it, but once the Crystal is retrieved Golbez takes control of Kain, who steals the Crystal and runs off. 

The party then heads back to the Upper World (after Cid attaches a drill to the head of the Falcon) and heads for Mysidia, where the Elder prays for something to help the party. 

That something is the Lunar Whale, the "Ship of Light from The Moon," which allows the party to fly to the Red Moon. Here, the party entered the lair of the Father and battled Bahamut to earn him as a summon. 

Rydia is the first human to earn Bahamut's help.

On The Moon, the party finds a palace where a man named Fusoya sleeps. 

Fusoya wakes up and explains that Golbez was being controlled by a Lunarian named Zemus the entire time. He then tells the real reason why Golbez is gathering the Crystals. 

The Crystals are the key to activating the Giant of Babil so that the Earth can be destroyed, and Zemus used Golbez to do it. 

The party returns to Earth with Fusoya. However, they are too late. The Giant of Babil has awakened, and began to go on its destructive spree. 

However, Cid, who was fully recovered, lead an army of leaders from all over the world, as well as friends of Cecil, to do battle with the Giant.

Cecil and his friends enter the Giant, and the party went towards the main computer, which, if destroyed, would stop the Giant. 

On the way, however, they had to do battle with the Archfiends again. 

After winning that battle, the party headed for the CPU and defeated it. 

Afterwards, an angry Golbez appeared, who was fuirous that his plans were thwarted. 

Fusoya knocked Golbez back to reality, and he learned that he was Cecil's brother. Fusoya and Golbez then headed to The Moon to fight Zemus, and Kain rejoined the party. 

On the Lunar Whale, Rydia was asked to leave the ship, and Edge egged her on about it. She was upset, but left anyway. However, she stowed away and headed to The Moon anyway, and convinced Cecil that she should join, as she believed that they were all fighting for a common cause, and that she was the only Summoner left. 

Cecil agreed to have her on the team again. They eventually headed to the Lunar Core and watched Fusoya and Golbez defeat Zemus. 

However, the hatred that was possessing Zemus, Zeromus, jumped out and attacked the party. With help from old friends, they defeated Zeromus.