Inside the &{template:atk} field exists two conditions
for hitting your target: "rname" (R-Name) and "rnamec" (R-Name C).
rnamec checks if the base roll goes within the critical success
threshold (commonly 20), and if so, to call a different ability than if
it were to roll normally. At this time, there are no field
options for "rnamef" (R-Name F) that calls for a unique ability if the roll is within a
Critical Failure threshold. Roll 20 does support varying critical
failure rolls via the cf argument (ie "1d20cf<3"), it would make sense if the template
utilizing critical success-checks the most had an option to utilize
critical failures as well. Not all DMs are going to use Critical
successes or failures of course, and Critical Failures don't
add or subtract any dice, so I can understand why it might be excluded as at that point there is no difference to just a regular roll. However where it
isn't useful in ordinary use, it can be vastly helpful for campaigns
where Critical Failures have unique consequences as opposed to a regular
or critically successful roll, as it would add a third ability
call to do anything with as opposed to simply running the ability call from "rname". It'd enhance the experience for those
who wish for it, and I think it would be a great addition overall.