> The escalation die represents a bonus to attacks as the fight goes on.
>
> At the start of the second round, the GM sets the escalation die at 1. Each PC gains a bonus to attack rolls equal to the current value on the escalation die. Each round, the escalation die advances by +1, to a maximum of +6.
Edit: It sounds like Blister Critters has generalized it so all attacks benefit, even those of non-PCs. And so it applies to more than just hit testing. Sounds simpler and more effective at ending combat conclusively ASAP.
Pretty sure that combat mechanic’s unknown origin is 13th Age’s [Escalation Die](https://www.13thagesrd.com/combat-rules/#Escalation_Die):
> The escalation die represents a bonus to attacks as the fight goes on.
>
> At the start of the second round, the GM sets the escalation die at 1. Each PC gains a bonus to attack rolls equal to the current value on the escalation die. Each round, the escalation die advances by +1, to a maximum of +6.
Edit: It sounds like Blister Critters has generalized it so all attacks benefit, even those of non-PCs. And so it applies to more than just hit testing. Sounds simpler and more effective at ending combat conclusively ASAP.