Siegfried (Japanese: Zeke/ジーク) is a Siberian Tiger that is blue and has a lightning sign at his forehead. He is Galleon's student, later works as Leo's teacher, who was his teacher's son. In AK series, he has an evolved form: Ninja Trained Siegfried. In the GAK series, he has a son named Bolt.
He first available in Version 3 as Boss Animal in Japanese and Version 4 in English and Taiwanese.
After finished his training in Ninja Village, Siegfried has an altered form, Ninja Trained Siegfried.
- Galleon is Siegfried's teacher, through this relationship, Scorch is his senior and Leo is his junior.
- Leo is the oldest son of Siegfried's teacher, Galleon. He then became the trainer of Leo.
- Zangetsu is the teacher of Siegfried when he had his training travel in Ninja Village. He has made Siegfried adapt his evolved form.
- Bolt is Siegfried's son who is a young hero, along with Rajan, the great-grandson of his teacher, Galleon.