Can you solve this riddle?

Disclaimer: I did NOT make this up.

First, think of a person who lives in disguise,
Who deals in secrets, but tell naught but lies.
Next, tell me what is the last thing to mend,
The middle of middle and the end of end?
And finally, give me the sounds often heard,
During the search of a hard-to-find word,
Now string them together and answer me this;
Which creature would you be unwilling to kiss?

(Harry Potter fans: SHHHHHHHH!!)