Learn Russian: Ничто не пугает меня в этом тёмном месте.

Ничто is in the Nominative case, which means it acts as the subject of the sentence. Here, 'nothing' is the thing doing the action (scaring). You use ничего (the Genitive or Accusative form) when 'nothing' is the object receiving the action, like in 'I see nothing' (Я ничего не вижу).

Why are there two negative words (ничто and не) in the same sentence?

Russian requires a double negative. Whenever you use a negative pronoun like ничто (nothing) or никто (nobody), the verb must also be made negative with не. Literally, this sentence translates to 'Nothing does not scare me.'

Is the ч in ничто pronounced like a 'ch' sound?

No, just like the basic word что (what), the ч here is pronounced like an English 'sh'. So, ничто is pronounced as 'ништо' (nee-SHTO).

Why do the words этом тёмном месте have those endings?

They are in the Prepositional case because they describe the location of an event (in this dark place). Место (place) is a neuter noun, so in the Prepositional case it becomes месте, and its matching adjectives take the -ом ending. If you were talking about motion into the place, you would use the Accusative case instead (в это тёмное место).