Waldstein, or Wald for short (The Mystery Senior of Powerful Arms, or in Japan as Strong-Armed Ancient), is a playable character and the main tritagonist in Under Night In-Birth and its updates. He returns as a playable character in BlazBlue Cross Tag Battle.
A hulking giant who has lived for more than a century, Waldstein once served the Licht Kreis, an organization which was dedicated to the protection of the Hollow Night and a rival to the Night Blade. He defected upon encountering Kuon, then the Night Blade's leader, and became the sworn protector of Linne from that point onwards, after Kuon had the Autonom Vatista to use her seventh wing to remove an overloaded EXS out of Waldstein’s body from completely turning into a Void, saving the latter’s life, yet the transformation progress turned Wald into a red-eyed hulking giant in progress as of today. Due to his defection from Litch Kreis, he is responsible for turning his former leader, Adelheid to despise men like himself, with Litch Kreis becomes a female only organization as of today, leading the ex-members of Litch Kreis, including its ex-male members to build their own new organization to be distant from Litch Kreis, known as Ritter Schild.
Waldstein continued to stay by Linne’s side even after the organization was ruined, in hopes to aid her end the Hollow Night and find the end she desperately seeks. As such, the duo have taken up residence in Hyde Kido's apartment, training him in the ways of combat as their investigation continues.
- Waldstein has color palettes of the following characters: Kum Haehyun (Guilty Gear), Taokaka (BlazBlue), Teddie (Persona 4), Carmine Prime, Adam Taurus (RWBY), and Amethyst (Steven Universe).