Notably, he was the owner of the unnamed gladiator in the Gladiator's Finale artifact set. After his gladiator's death at Vennessa's hands, he would eventually mastermind behind the deaths of the Dragonspine expedition team primarily comprised of young Mondstadt aristocrats.
Eberhart was cruel and manipulative, using his glib tongue and promises of fine rewards to entice his unnamed gladiator into continue fighting — and killing — for his sake. He uses this sort of manipulation later on to persuade the rest of the expedition team that those lost in the snowstorm would be able to make it back safely, and incite them to investigate a different location before their intended one in the hopes of reducing the numbers of the remaining members of the expedition. Eberhart believed that the ends were more important than the means, and was willing to stoop to all sorts of vile methods to achieve his goals:
"So what if those who came after should despise me? I will do anything to achieve my goals."
Little is known about Eberhart's origins or lineage, but he was an illegitimate heir to an aristocratic family, likely Landrich's. According to the author of the Ancient Investigation Journals, this may have led him to plot a rebellion against his fellow aristocrats.
Eberhart owned an unnamed gladiator, and manipulated the gladiator into continuing to fight for his entertainment even after the man had won his freedom. This gladiator would eventually fall at Vennessa's hands.
Some time before the expedition to Dragonspine, Eberhart incited his legitimate brother Parsifal to become a phantom thief and then eventually deceived him, forcing him to flee. Somewhere in this same time period, Eberhart studied under a certain witch, becoming her disciple to better learn how to use a spear. Learning her ability to target fatal flaws, he used her love of the phantom thief as an opportunity to betray her and kill her. It's unclear what his reason was for killing the spear-wielding witch, but his reason for causing his brother to flee was so that he had a better chance of claiming legitimacy.
Some time after the death of his gladiator, Eberhart would embark on an expedition to Dragonspine alongside Ingbert, Nick, Luther, and some other unnamed members. However, by this time, he already conspired to betray the aristocrats, and laid several well-planned traps that dwindled the group's numbers down to only himself, Ingbert, and Luther. He attempted to slay Ingbert and Luther personally, and while he succeeded in taking down Ingbert and mortally wounding Luther, was gravely injured himself. He made it back to his boat with little trouble and left for Mondstadt, knowing that if news somehow made it back to Mondstadt, then Priscilla would light a torch at Stormbearer Point to warn him. According to Luther, this plot to kill Ingbert was probably to move ahead in the line of succession.
According to Stevens, there's no record of Eberhart returning to Mondstadt, so it's unknown whether he survived and where he went. It's unclear whether the revolt he was going to be part of was Vennessa's rebellion or something entirely different, and whether he did manage to take part in it or not.
- Eberhart was likely the young noble that had the Royal Spear crafted and practiced with it in secret, as many of the details match up.