Without a doubt the Slann are one of most important part of the Lizardman army. In some ways without the Slann there would be no lizardmen. What I would like to have you input of is how do they sound what they talk. Would the sound the same? Or are they different? Could they be very loud or deep?
I've always pictured it as deep, sonorous, prolonged croaks, possessing the fluidity of chanting, while still being distinctly rough and low.
+1 We're talking about creatures that barely move on their own, who have skink attendants for pretty much everything. Do we really think they are going to open their mouths to speak when they could just do it all with magic? Fat, lazy, unimaginably powerful toads... Yup, that's our leaders!
Slann communicate telepathically among themselves. Slann can communicate telepathically with lesser Lizardmen but they don't do it much outside of Arcane Vassals. It takes a lot of effort to communicate in a way lesser minds can understand. Also, it's usually usually painful and invasive for non-Slann recipients of their telepathy unless Slann take great pains to be gentle (which they can't do while multi-tasking in a battle, linkeh=http://www.lustria-online.com/viewtopic.php?f=32&t=14663]as in my story Legacies[/URL]. So if they need to communicate to lesser beings in a normally talk. In the rare instance the Slann is talking to an enemy, invasive telepathy is the norm. This is better than what I was picturing ("ummm, the sound like frogs"), so I'm going to steal your description for my fluff pieces. However I will add that Slann are usually quite terse. It varies from Slann to Slann. Lord Desserex is so talkative by Slann standards that he would only mildly annoy a hypothetical Human who could understand High Saurian. he could pass for terse human with the right illusion spells. Lord Merestar is so terse the hypothetical Human would assume he's dead.
Use away. And yes, I think Slann are often terse, but I've always thought of Saurian as not being a very economical language. That is, even relatively simple concepts require a lot of "language" to get across the message. Saurus and other worker or warrior class lizards maybe have limited vocabulary because they have limited access to the language in everyday use. Slann, who live for thousands of years, can afford to express the full depth of Saurian over as much time as they need, relaying complex ideas and concepts they exist beyond the understanding of most other mortal beings.