Não até que já esteja sobre eles
Ênfase minha:
'What happened away up there at the door?' [Gimli] asked. 'Did you meet the beater of the drums?'
I do not know,' answered Gandalf. 'But I found myself suddenly faced by something that I have not met before. I could think of nothing to do but to try and put a shutting-spell on the door. I know many; but to do things of that kind rightly requires time, and even then the door can be broken by strength.
'As I stood there I could hear orc-voices on the other side: at any moment I thought they would burst it open. I could not hear what was said; they seemed to be talking in their own hideous language. All I caught was ghâsh; that is "fire". Then something came into the chamber - I felt it through the door, and the orcs themselves were afraid and fell silent. It laid hold of the iron ring, and then it perceived me and my spell.
What it was I cannot guess, but I have never felt such a challenge.
[...]
'Ai! ai!' wailed Legolas. 'A Balrog! A Balrog is come!'
Gimli stared with wide eyes. 'Durin's Bane!' he cried, and letting his axe fall he covered his face.
'A Balrog,' muttered Gandalf. 'Now I understand.' He faltered and leaned heavily on his staff. 'What an evil fortune! And I am already weary.'
Fellowship of the Ring Book II Chapter 5: "The Bridge of Khazad-dûm"
Por que vale a pena, no texto, o próprio Gandalf propõe Moria como uma alternativa para Caradhras:
'There is a way that we may attempt,' said Gandalf. 'I thought from the beginning, when first I considered this journey, that we should try it. But it is not a pleasant way, and I have not spoken of it to the Company before. Aragorn was against it, until the pass over the mountains had at least been tried.'
[...]
'The road that I speak of leads to the Mines of Moria,' said Gandalf. Only Gimli lifted up his head; a smouldering fire was in his eyes. On all the others a dread fell at the mention of that name. Even to the hobbits it was a legend of vague fear.
Fellowship of the Ring Book II Chapter 4: "A Journey in the Dark"