- "Could it be... you know of Aura?"
- — Harald —
His first appearance is of an "old man floating upside down" though his voice betrays this, as well his avatar does not appear old at all, upon closer inspection of the "chair" it is a vague humanoid shaped creature, though as it does nothing it is probably just that, a chair.
His second appearance is that of a large stone with inscriptions on it. When he talks, the inscriptions turn rainbow-colored.
His third appearance was similar to his first, though only the human shaped chair remained. Any traces of the man who had sat in it were gone.
His personality is one of sadness and regret, as Harald's AI's are to have a manner of intelligence this one simply repeats himself. It is believed by some that until his mind is averted by a question or a statement that catches the AI's "attention" he would remain "broken."
Kazushi Watarai reveals AI Harald's existence while he is discussing the history of Δ Hidden Forbidden Holy Ground and the rumored "ghost of the church" who existed in the early versions of the game and was believed to have vanished in the transition from Fragment. However, the vagrant AI Lycoris reveals that this copy of AI Harald was still present in the cathedral just a few days before the events of the book. Due to a translation error, the English version claims that this "ghost" is a manifestation of Morganna Mode Gone.
Prior to the events of SIGN, AI Harald sent a post out to The World's BBS. The post was originally written in German, and was deleted soon after being posted. When translated, it read:
- "When the Twilight Eye doth open, so too shall the path to me.
- Discourse with me and against that power fight.
- When the key that overturns all is possessed everything shall unfold."
This post started rumors of a legendary item hidden in The World, the Key of the Twilight. The post also contained a clue about how to unlock the Twilight Eye at Δ Hidden Forbidden Holy Ground, which allowed access to the area Θ Bitter Fantasy Mirror World where a copy of AI Harald was hidden. Bear, Mimiru, Tsukasa, and BT were able to make contact with the AI, receiving information regarding Aura. Later in the series, Bear, Mimiru, and Subaru went to meet him again; however, their visit drew the attention of Morganna who was able to delete that copy of the AI.
Kite encounters several messages left by Harald over the course of the Games, and hears his voice in a few dungeons. However, he doesn't actually get to meet him until the final game. In .hack//Quarantine, the AI Tartarga mentions in an email that he talked with an AI version of Harald at the field Δ Reincarnated Purgatorial Altar.
After a confusing conversation with him and the reborn Aura, Lios tells Kite that there is a huge mass of data coming that way. However, it is not the Cursed Wave. The rock shatters and then Cubia appears.
In a flashback in XXXX, young Cubia sees Harald with a young Aura. When Aura notices Cubia and asks who he is, Harald dismisses him as "just some trash data left over from when you were born".
A Harald AI was found deep inside the Forest of Pain event, a nearly impossible maze-like field filled with powerful monsters. Of all the people who attempted the event only two, Taihaku and Haseo, managed to reach the Harald AI. Harald's room was reached by drawing a weapon (tailored to the class of the person viewing it) from a boulder. This would teleport the person to the room containing Harald.
Harald would then ask the person about his daughter, who he had not seen for a long time. Taihaku responded that he didn't know Harald's daughter, but that he wished her well. As a reward for his politeness Harald allowed Taihaku to keep the weapon he'd drawn, a unique and powerful Steam Gun. Haseo responded with anger, saying that he didn't know, nor care about his daughter. To him Harald denied him the weapon, and instead shot him with a bolt of black lightning, which forcibly upgraded him to his final Adept Rogue form, an act that eventually hindered Haseo more than it helped. Shortly after Haseo completed the event, the field was discarded. What became of the Harald AI afterwards is unknown.
At the end of the Forest of Pain, AI Harald appears again to Haseo. Similar to .hack//Roots, only the humanoid chair is visible, but he asks Haseo a series of questions regarding whether or not to take a path of difficulty or ease. After considering Haseo's answers, AI Harald states that he will not gift him with a weapon, but will instead grant him one wish.