Wildling

When you take this feat, and at the start of each subsequent game session, you may roll a d20 and set it aside in a designated area with the rolled face up; this is your Wild Die. When you have just rolled one or more d20's for an attack, saving throw, or ability check, you can choose to exchange your current Wild Die (with its rolled side up) for one of those d20's before determining the outcome of the roll. The d20 you replaced (with its rolled side up) is now your Wild Die. You may use this feat up to once per turn a number of times equal to your proficiency bonus per long rest.

For instance, if you rolled a 15 for your Wild Die at the start of a game session and later rolled a 20 for an ability check, you could choose to swap out your current Wild Die for the 20, which becomes your new Wild Die. The ability check would then resolve using 15 as the rolled result. Sometime later, you might make an attack roll and choose to exchange the rolled d20 with your Wild Die of 20 to score a critical hit.

This feat may be taken mutliple times and may combine with the class feature of the same name, with each instance allowing you to use this feature an aditional number of times equal to your proficiency bonus per long rest.