Credit goes to YEYP.
This Lugia is a female, just has no female or women parts (which i'm ok with)

Mercury and Lavender's long lost younger sister, Venus Quicksilver. She' almost exactly like her eldest brother, but she's not as crazed as Mercury is.

Name: Venus Quicksilver
Occupation: Sea Guardian and Warlord.
Title: Prettiest Lugia of the Seas.
Movesets: Diaper Breathe, Aeroblast, Psychic, Mist
Personality: Calm, Kind, Stern. Goofy
Goal: To Help Pampaku and Mercury to make amends

Story:
Her parents were lost during Kroko's raid on the Lugia village and the nest where their parents eggs were kept were also taken and put in a special incubator that prevents them from hatching. Some after Azure's descent into being a Shadow Lugia, he saw the horrors that the Lugias went through and did everything he could to rescue as many Lugias and eggs, which were successful. Lavender saved several Lugias and even his families eggs (he was confused why there were only 9). One of those eggs was his sister.
Many years after Kroko's defeat and the Lugias liberated, the eggs hatched and Venus was born, even the fortune teller returned many years later and she was soon picked up by the Kanto Trio (who got a harsh scolding from the diaper gods after the last guardian). They put her through the same training regiment as Mercury, so she became very powerful and even has great resistances to her weaknesses. She soon became the next guardian of the sea, but was a little more laxed, she was free to do whatever she wants as long as the sea shrines were safe.
She soon saw Pampaku causing some trouble and actually befriended, but she overheard the name 'Mercury Quicksilver' in a harsh mad tone, so she decided to hide her last name and actually befriended him. Pampaku even trained her to use diaper breathe at the same level as Mercury. She gained Pampaku's trust by playing a game with Sandoku so he did drop his guard about his connection with Mercury. Venus even went to her eldest brother Mercury for his side, both were stubborn to admit it. So she made it her life goal to help the duo make peace and be friends again since she found out that Mona and Kimo secretly hang out with Pampaku so Mercury won't be upset.
She befriended a Mew who was being hunted by poachers and the two became fast friends due to both being the victim of hunts. Despite being a legendary, Mew won't fight due to Mews having a powerful playful history. The Mew is mostly known to teleport themselves to the sea shrines to keep an eye on them, or to go to one of the 4 island kingdoms to catch up with Mercury and Lavender.
End

Relationships:
Audry- The Mew who soon became her personal diaper and help her teleport around the sea and even trains with her.
Mercury Quicksilver- She really admires her eldest brother for playing his part in the Siwa war and likes how he wields one of its national treasures, the Aqua Spear.
Azure (Lavender) Quicksilver- Lavender saved her as an egg during his time as Kroko's servant, but rescued many Lugias before his defection. She respects Lavender, but is still surprised that he became a Shadow Lugia.
Pampaku- She befriended Pampaku to help figure the issues behind their sunken frienship, she does like to see Pampaku turn others into diapers. She even spars with him even though she never wins.
Ragtag Rogues- The ragtag rogues did see how she treated Pampaku and Sandoku with kindness, so she's ok with them and willing to even help her. She spars with them also and despite their training, they still have a hard time defeating a legendary.

Might plan a backstory for her when more characters come into play, she's exactly like Mercury in strength and power. Along with an identical personality and has goofy side for turning others into diapers for those who insult her family or even trying to capture her Mew friend since anyone caught going after a Lugia ends up with the pamp penalty.