Technically, a sinus infection (sinusitis) is not an infection, but it refers to the inflammation or swelling of the tissues that line the sinuses. Such swelling or inflammation occurs when the sinuses get blocked and filled with fluid (mucus).
Master Investigators Box. The Master Investigators Box holds the keys (which are four rings, Katarina's Ring, Treoy's Ring, Balwen's Ring and Pithi's Ring) to the Daedric Relic. The chest is located on the wall to the North/West side of The Arcanaeum. The key to the chest is located in the Midden Dark on a table in the room with the Daedric Relic, on top of a book called Midden Incident Report. Once the rings are acquired they can then be placed on the Daedric Relic to release Velehk Sain.
The Violet Citadel is the location of the Grand Library. The Violet Citadel also contains the Arcane Vault which houses Dalaran's most powerful artifacts. It was from there that Teron Gorefiend stole the Eye of Dalaran and killed Sathera.