Val'anyr - Hammer of the Ancient Kings

Val'anyr, Hammer of the Ancient Kings. This is a One-Hand Mace and even if the stats aren't known yet, it should only be available in a healer version. The mace itself won't drop from any boss, players will be able to rebuild it through an Atiesh-like questline started by the Shattered Fragments of Val'anyr dropped by most of the bosses in Ulduar-25.

You will need 30 Fragments to reforge the Hammer of Ancient Kings, just like the quest item you can drop Fragment of Val'anyr from most of the bosses in the 25-man version of the instance.This is done during the fight against Yogg-Saron (the final boss of the instance) through the Val'anyr Hammer of Ancient Kings quest.

We can assume that Yogg-Saron uses Deafening Roar during a late stage of the fight. There are two quests related to the Val'anyr, the first one is Ancient History started by the Shattered Fragments of Val'anyr, followed by Val'anyr, Hammer of Ancient Kings.