Joe finds his Crest of Reliability hidden under a soccer goal in the colosseum.
Believing that danger and energy are the keys to evolution, Tai stuffs Agumon with food and then intentionally puts himself in harm's way to trigger a transformation. Digimon Adventure Episode 16
While wandering the desert, the DigiDestined are lured into a Roman-style colosseum by Etemon. Tai, having recently acquired his Crest of Courage, becomes obsessed with forcing Greymon to evolve to the "Ultimate" level to defeat Etemon. Joe finds his Crest of Reliability hidden under