HT665: Erio is a NPC in Xenoblade Chronicles X. She is a Definian first seen in her true form on an island near the West Gate Plain in Primordia at the end of the Normal Mission Attack on Biahno Hills. At a later time, she can be found in the Central Industrial District of New Los Angeles. She is found later near Central Melville Street in the Commercial District.
HT665: Erio infiltrated New LA sometime after it crash-landed on Mira by taking the identity of a girl named Suriella who died during the crash. However, due to her time with humans, she started to have doubts on the Ganglion as many people liked and respected her in a way she never felt before. Due to this another Definian named DE913: Dieara later infiltrates New LA by killing and then taking the identity of a man named Clemons roughly a week before the normal mission Attack on Biahno Hills takes place, and after doing so she started to give false information to BLADE so they would sent operatives to their deaths. however, HT665: Erio sabotaged DE913: Dieara's scheme and forced her to escape while HT665: Erio (posing as Clemons) gave the location of the real Clemons' body to Cross. After discovering the truth, HT665: Erio and DE913: Dieara escaped to a small island outside of the city where DE913: Dieara accused HT665: Erio of betrayal and attempted to kill her but was saved by Cross, after saving her, she revealed what happened to the real Suriella and why she changed her mind on humans. Eventually, Lara Nara arrived and took HT665: Erio into his custody as a personal favor.
The player will later encounter HT665: Erio in the city, now a citizen thanks to Nara. She will ask the player to kidnap the Definians' mother: a cybernetic being known as Fortun to force her sisters into leaving the Ganglion's ranks, triggering the mission Good Fortun. After defeating SG002: Slenna and taking Fortun to New LA to be hacked by Professor B, HT665: Erio will sent the player to the Ganglion Antropolis on Cauldros to take out the three leading Definian sisters in the mission Definian Downfall. During the mission, HT665: Erio asks the player about what to do with Fortun after hearing all the information they needed from her, and the player is given the choice to destroy Fortun or spare her.
After completing Definian Downfall, HT665: Erio will take a human appearance simply known as Erio whose gender will be opposite of Cross's.
- Main article: Gwin (The Gauntlet)
An opponent disguised as Gwin is fought at level 56 at the Outfitters Test Hangar in the Industrial District during the fourth battle of The Gauntlet. Right before the battle, the opponent's dialogue heavily implies that it is not really Gwin, and HT665: Erio reveals her true identity immediately upon defeat, having disguised herself as Gwin.