Adena was one of Ayden's first Pokémon and Kai's mother.
Adena was Ayden's second Pokémon, whom she received from Professor Oak as a Charmander. Adena accompanied Ayden to many regions, where she eventually evolved into Charmeleon and subsequently, Charizard. Now, she remains at Ayden's home in Phenac City, while her child, Kai travels with Ayden.
As a Charmander, Adena was very shy and reserved. She was not particularly enthusiastic about battles and often relied on Azreal to do most of the hard work. However, when she evolved into a Charmeleon, Adena's confidence boosted significantly. She was more sure and confident in her battling abilities and now relished the feeling of being in a battle. However, this did result in a short period of rebellion. Her love for battle resulted in her often disobeying Ayden's commands in battle. She became so focused on the fight itself that she forgot about strategy. After suffering a loss to a gym leader because of her rash attitude, she realized that she had to listen to Ayden if she were to win effectively.
As a Charizard, Adena possesses great strength and speed. She prefers getting an aerial advantage over her opponents and often remains in the air, hovering over the battle field. However, she is not afraid to get up close to her opponents. She often uses Sunny Day in order to boost the power of her Fire-type attacks and Attract to disorientate male foes.
Adena was originally given to Ayden by Professor Oak when the latter traveled to the Orre region to collect the research notes of Yvonne Holly, Ayden's deceased mother and his best friend from college. As a thank you for Professor Holly's notes, Professor Oak gave Ayden a Charmander and Ingrid a Bulbasaur.
At some point during Ayden's travels to the Kanto region, Adena evolved into Charmeleon. She would evolve again sometime after arriving in Johto.
Some time later, Adena laid an egg, which later hatched into a young Charmander. Adena decided to remain at Phenac City and no longer travel with Ayden, allowing her child to go instead.