Horadric Strongrooms are micro-dungeons in Diablo IV, introduced in the Sins of the Horadrim update. They are fast-paced, timed micro-dungeons where players slay monsters to build up Horadric Attunement. The higher the attunement by the session's end, the greater the rewards. If a player dies during the run, the available time is reduced. When the timer runs out, the player must defeat a boss to earn the loot gained from the run.
The strongrooms can be found in Nightmare Dungeons and Escalating Nightmares. The higher the difficulty, the greater the chance a player has of finding a strongroom. At the start of a run, players can choose from one of three Horadric pillars which adds affixes to the monsters.