Giselle Gewelle is a Quincy and member of the Wandenreich's Sternritter, holding the designation "Z." He's best known for his zombie-themed power and his unsettling ability to control those marked by his blood.
Visually, Giselle stands out with long dark hair that reaches his lower back, complete with two strands that stick up like antennae. His Sternritter uniform is mostly standard white issue—a long-sleeved trench coat, white shoes, and black leggings—but distinctly his own.
His power, called The Zombie, works by splattering his blood on a target, which turns them into a controllable "corpse" that obeys his commands. There's a catch though: this doesn't work on other living Quincy, only those already dead. What makes the ability especially useful in combat is that Giselle can harvest flesh from corpses to heal his allies' wounds, essentially weaponizing the dead in multiple ways.
Something fans often note is Giselle's distinctly feminine appearance and mannerisms, which led to plenty of speculation about the character. Tite Kubo confirmed in a Q&A that Giselle is male, settling the debate pretty definitively.
Content compiled by AnimeList.moe from publicly available sources.