Who are the Sternritter, and what is their role in the war?

The Sternritter are the elite Quincy warriors, handpicked by Yhwach to lead the Quincy invasion of Soul Society. Each Sternritter possesses a unique ability known as a 'Heilig Pfeifer' (Holy Bow), which allows them to manipulate spiritual energy in extraordinary ways. They represent a significant threat to the Soul Reapers due to their power and strategic planning.