I have two theories on what may have happened to Banon. The first one is that during the destruction of the world, Banon was fortunately out of Vector looking for a flower to give to a girl he liked. Unfortunately, the land cracked around him and he was stranded on a lone mountain range on an island in the middle of nowhere. As time passed, Banon learned how to adapt to his new lifestyle by eating various insects and rabbits. He was constantly allured into trying to eat the flower, but there was always a part of him inside that said they would meet again. After about 9 months, Banon had become a full beast not unlike Gau, however, his skin had turned bright blue due to the mild poisoning in the nearby water. Luckily, he was immune because of his health spell. Then, about a week later, Banon fell off of his mountain top and into the ocean. He thought about saving himself, but realized that it was futile and just relaxed and let the ocean take him. Thinking he was dead, he awoke a couple days later expecting to be in heaven. Unfortunately, he was just in the middle of a desert, perfectly alive, though his skin had changed again, this time to a dark green. He had also shrunk from the saltiness of the water. In addition, his hair began to grow out sharp and pointy all over his body. Thus, Banon became Cactaur.

The other theory is that he just died sometime during the end of the world.