This clever looping mechanism relies on a brilliant mutual admiration society between a pair of dragons. Once you use Helm of the Host at the start of combat to spin out a nonlegendary token copy of Enduring Scalelord, you simply place a stray +1/+1 counter on either the original or the newcomer. That initial counter triggers the *other* Enduring Scalelord, which receives its own counter in response, which in turn triggers the first one right back. This creates an unstoppable cascade of mutually triggered growth, resulting in infinitely large creatures ready to crush your opponents with sudden, overwhelming power.