You get the option to bring back 1 spell/ability from a previous expansion and use it now going forward.
Doesn't matter about class balance or class fantasy reasons. Doesn't matter if it was a base ability or granted from a talent option now since removed.
Blank check choice. What do you choose?
My personal is Claws of Shirvallah talent for Feral Druids that was available during WoD.
Couple of reasons: I loved being a fucking were-cat-man, allowed use of Druid healing spells while in were-cat-man form, and the Versatility buff promoted an auto-attack/Shred spam playstyle apart from a focus on Bleed effects.
But mostly the fucking were-cat-man.