Classes like RDD are available but not selctable at the start of SoU,when are they available to be selected??
You have to meet the requirements for the RDD prestiege class. In this case the RDD requires 8 points in the 'lore' skill and at least 1 level of sorcerer or bard. After this you'll be fully multi-classed so you can take no more class options.
Other prestiege classes have different requirements. The champion of Torm would be another good one for a pally. Check the manual or you can find a really, really good, comprehensive PDF file here:
Neverwinter Grimiore Scroll down the page to download the file of the same name....
Egin, this should help with your character builds too. <img src="/ubbthreads/images/graemlins/up.gif" alt="" />