As title said. I have some spoken vokals I need to change into 'troll/monster' speech. The usage do not justify hiring someone to do it for me.

I looked into some 'AV voice changers', but I was a bit disapointed of the quality, seems those where made for kids in voice chats.

So, anyone know any software a bit more professional to do this, or some tips what settings I should tweak in a standard audio post app.

I searched the web for tutorials and software, but did not find anything I could use.

Any pointers greatly appreciated !

Dropping the pitch by -13cents is a good start, with just a whisper of chorus to smooth out the edges of the transformation, you'll likely want to add another transformation of a fifth (-7) and mix it in very, very quietly to give it body.
Some apps do this well, others don't.

Douglas, thanks, I'll try playing around with that as a base.

In addition to Douglas' suggestions, you could try a bit of an amp simulator or lo-fi plugin, particularly if you need an element of menace (might add a nice flavor to the second, lower pitched track)

One option is to use the dialogue as a modulator signal in a vocoder and run white noise or rumble into the other channel then pitch shift it all over the place.

This can work quite nicely.

There are some vst plugins called vocalizers that work pretty well. There's TONS of freebies on the web. Here's one:
http://www.analogx.com/CONTENTS/download/audio/vocoder.htm