There's been quite a bit of debate and confusion over the nature of Mordremoth, and this seems like the perfect chance to get clarification.
Throughout the end of Heart of Thorns, we're presented with the notion that Mordremoth does not have an actual physical body - that he is purely a being of mind. Though at the same time, the Mouth of Mordremoth acts and, sometimes, is referred to as the Elder Dragon. At other times, it's treated as merely a powerful champion of Mordremoth. In Vabbi, the Commander tells students of how Mordremoth died: impaling itself on a tree, which is how the Mouth of Mordremoth died.
So to the question: What is the connection between Mordremoth and the Mouth of Mordremoth? Is the Mouth Mordremoth's actual body, merely a part of it, or not at all? If the second, what is the rest? If the last, does Mordremoth have a physical body at all?
And an addendum: Artist Marcus Jackson calls the Mordrem Spitfires "Lesser Mordremoth Heads". Is this solely in reference to their appearance, or are Spitfires part of Mordremoth (too)?
Addendum 2 because similar topic: The dialogue with Laranthir and during Hearts and Minds implies that the Mouth of Mordremoth is fought multiple times; at least three times to be specific. Is this the case?
My theory on the matter, in spoilers to not influence the answer,
(EDIT: Odd, why is the spoiler showing up as a block of gray one must highlight and not the usual spoiler button? Did the forum get changed?)
(EDIT2: And it fixed itself. Curious.)