Pan often takes the form of a cat when Lyra is nervous, afraid or angry. Lyra herself is described as being cat-like, especially in reference to her wildness at the start of her journey. It is also one of the things that ties her to Lord Asriel, her true father, who is often described as looking like a lion. He has a snow leopard for a dæmon.
Manganese is a metal that has many important alloy uses, especially in rust prevention in stainless steel. However in large amounts, especially through inhalation, manganese can be poisonous to mammals and can cause sometimes irreversible neurological conditions, including psychiatric and nervous disturbances known as "manganism".
Its physical effect on the mental health of human beings is especially relevant in the context of Northern Lights, when we consider what the alloy of manganese and titanium is used for.
A ghoul is a folklore monster, most often associated with the consumption of human flesh. The word is derived from the Arabic word ghul, "to seize".
In Arabic folklore, the ghūl (literally "demon") is a shape-shifting demon found in the desert that preys on unwary travellers and children.
The word ghoulish is used as a derogatory term for a person who takes an unhealthy interest or pleasure in the macabre, which is the meaning here.