The 26-year-old centre, who has signed from Carmarthen Quins on a month-long loan, commented: "The step up from Premiership to British and Irish Cup is big and it will be the same again (from British and Irish Cup to regional rugby) but I am looking forward to it. It will be a big challenge at Ulster but I can't wait and feel I am ready for it.
"I'd like to think that I am a direct centre and that I put my tackles in, I've played 12 most of my career but can also slot in at 13.”
Including Williams, Director of Rugby Lyn Jones, has made seven changes to the team that faced Newcastle Falcons in Round two of the European Rugby Challenge Cup.
Jason Tovey, who recently played for Premiership side Cross Keys at fullback, has made the move into the back three and is joined by wings Matthew Pewtner and Aled Brew. The centre pairing takes on the new shape of Rhys Williams and Ashley Smith. Halfbacks Angus O'Brien and Richie Rees retain their places as fly-half and fullback.
The front row sees the return of Boris Stankovich and Thomas Rhys Thomas who join tight head prop Dan Way. They are joined in the front five by locks James Thomas and Rynard Landman, the latter taking on the role of captain. The back row has two changes as Lewis Evans is joined by young gun James Benjamin and British and Irish Lion Andy Powell.
The replacement bench has five changes as youngsters Elliot Dee, Scott Andrews, Ollie Griffiths, Geraint Rhys Jones and Ashton Hewitt join Owen Evans, Lloyd Fairbrother and Jonathan Evans.
Newport Gwent Dragons Team to face Ulster
Jason Tovey, Matthew Pewtner, Rhys Williams, Ashley Smith, Aled Brew, Angus O'Brien, Richie Rees; Boris Stankovich, Thomas Rhys Thomas, Dan Way, James Thomas, Rynard Landman (c), Lewis Evans, James Benjamin, Andy Powell.
Replacements: Elliot Dee, Owen Evans, Lloyd Fairbrother, Scott Andrews, Ollie Griffiths, Jonathan Evans, Geraint Rhys Jones, Ashton Hewitt.