Simple RAW for 5e V: The Disadvantage Strikes Back

[Dualswinger]

Q. 288

A path of the beast barbarian can grow a tail to increase their ac but I can’t see an end clause. For how long does the ac bonus from the tail reaction last?

Tail. You grow a lashing, spiny tail, which deals 1d8 piercing damage on a hit and has the reach property. If a creature you can see within 10 feet of you hits you with an attack roll, you can use your reaction to swipe your tail and roll a d8, applying a bonus to your AC equal to the number rolled, potentially causing the attack to miss you.