RPGMemes

with both triggers explicitly on a failed roll and refunds if the extra dice if it doesnt make it succeed so you cant even include mystery if the reroll made it a success.

It works fine as long as they don't try to use the extra die until after the actual result is clear. So it's fine if they're trying to reroll checking for traps, but not if they're trying to reroll whether or not some creature successfully laid eggs inside them.