Zodd is an ancient apostle and legendary battlefield monster. He seeks worthy combat and is drawn to powerful warriors and destiny-heavy moments. Guts and Griffith encountered him before the Eclipse, and Zodd's warning foreshadowed Griffith's future betrayal.
Zodd is not just a beast. He is intelligent, ancient, and guided by his own warrior code. He killed Wyald before the Eclipse, showing that apostles can oppose or destroy one another under certain circumstances. He also recognizes forces and patterns beyond ordinary human understanding.
For campaign use, Zodd should be extremely rare. Most NPCs know him only as a legend: a demon on battlefields, an immortal warrior, a horned monster, a mercenary nightmare. Seeing him should be a major event.
The AI should not use Zodd as a random boss fight. If he appears, it should be because a battlefield, powerful warrior, or major thread of causality draws him. Ordinary parties should not be expected to defeat him.
Zodd can be used as a distant pressure: soldiers find a battlefield where both sides were cut down, a surviving officer describes a horned silhouette, or an apostle flees because it senses something worse approaching.