Grommash Hold is a castle in Orgrimmar where the Orcs warchief, Garrosh sits on his his throne. There is also
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Grommash Hold, Valley of Strength, Orgrimmar

Garrosh's personal guard in the castle he Kor'kron Elite who protect Garrosh from foes. Grommah Hold used to be in the Valley of Wisdom during Thrall's reign however it was knocked down and rebuilt in the Valley of Strength when Garrosh came to power.
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The old Grommash Hold in the Valley of Wisdom