>>282069909
After Halkenburg failed at killing his father and himself, he developed a Hatsu of his own (said to be granted by his GSB).

Halkenburg's Guardian Spirit Beast is a Symbiotic-type Enhancer. His GSB can gather Halkenburg's supporters aura in a big amount of nen.

The arrow ability is Halkenburg's own ability. His GSB grants him a huge amount of aura when he uses his ability when his supporters are by his side. His attack is unstoppable and Halkenburg is speculated to be invincible during casting it.