Some complicated clues

I am mud that will trap you. I am a colloid hydrogel. What am I?

Take the first half of me and add me to this:

I am dangerous to wolves and werewolves alike. Some people even say that I am dangerous to unholy things. Use the creator of Poirot to find out: What am I?

Now, take another word for your current result and only take the first four letters of it...

To fill in the rest of the letters, answer me this:

I am a fighter of luck, or something like that. What am I?

Take my last three letters, and to find out which letter to add to the beginning, answer me this:

I am trapped in the middle, and dead unlucky. What am I?

Finally, replace the last letter of what you have with this:

I am everywhere, what am I? 5

What are you left with?

I am mud that will trap you. I am a colloid hydrogel. What am I?

@Mohirl found it was Quicksand

Take the first half of me and add me to this:

First half is Quick

I am dangerous to wolves and werewolves alike. Some people even say that I am dangerous to unholy things. Use the creator of Poirot to find out: What am I?

This is Silver

Now, take another word for your current result and only take the first four letters of it...

Quicksilver is also known as Mercury, so MERC-

To fill in the rest of the letters, answer me this: I am a fighter of luck, or something like that. What am I?

A fighter of luck may be a MERCENARY

Take my last three letters, and to find out which letter to add to the beginning, answer me this:

So we have -ARY

I am trapped in the middle, and dead unlucky. What am I?

The middle of the alphabet is either M or N, and dead unlucky clues the 13th letter, M. This leaves us with MARY.

Finally, replace the last letter of what you have with this: I am everywhere, what am I?

Potentially E, as the most common letter of the alphabet

What are you left with?

MARE

• Oooooohhh - You're so close that you can taste it! +1 Not entirely there yet, though... Jul 24, 2019 at 19:37
• @INTERESTING which steps are incorrect, if I might ask? I’m not sure starting at the fighter of luck step. Jul 24, 2019 at 20:21
• Umm... You messed up a little bit past halfway through! (The last four spoilers are incorrect...) Jul 24, 2019 at 20:42
• Last four or last five, @INTERESTING ? Jul 24, 2019 at 21:33
• Sorry I meant last three. Jul 24, 2019 at 22:08

Partial in progress

I am mud that will trap you. I am a colloid hydrogel. What am I?

Quicksand

Take the first half of me and add me to this:

So quick + the next answer

I am dangerous to wolves and werewolves alike. Some people even say that I am dangerous to unholy things. Use the creator of Poirot to find out: What am I?

Agatha Christie? AC? (Silver) bullet? Answer forms a compound word after 'quick'

Now, take another word for your current result and only take the first four letters of it...

To fill in the rest of the letters, answer me this:

I am a fighter of luck, or something like that. What am I?

Take my last three letters, and to find out which letter to add to the beginning, answer me this:

I am trapped in the middle, and dead unlucky. What am I?

Finally, replace the last letter of what you have with this:

I am everywhere, what am I? 5

• rot13(Ntngun Puevfgv... Nt vf Fvyire) Jul 24, 2019 at 15:54
• Cheers, I'm assume that's what the intended answer is, but it's a bit of a stretch for me Jul 24, 2019 at 16:18
• @SteveV is correct... Jul 24, 2019 at 19:39