According to the rule “Boons”:

An Adventurer with 0 Boons cannot use Battle Actions.

This still makes no reference to Human Battle Actions, and therefore continues to include the Monster. Kevan’s first Battle Action was as a Monster Vanguard, in part thanks to the fact that this rule said “Combat Actions” at the time; when this was fixed, however, Kevan continued to play without first Introducing Himself to define his Boons as an Adventurer.

It would seem that this forces us to repeat most of the past Battle yet again... Though, to be honest, I’m getting tired of all this back and forth. If Kevan would just take his Boons now, I’d be happy for us to continue with the new Battle.