There have been a lot of theories about exactly who Clarissa might be - but Reign Season 1 Episode 11 put them all to rest:
She's an illegitimate daughter of Queen Catherine's with her lover Viscount Richard Delacroix. Whoops!
Some heads are gonna roll!
Well, to be technical, one already rolled, and the Viscount's might have rolled by now. Catherine's was already on the schedule before Henry knew about her bastard daughter... or her attempt on Mary's life. Catherine really wants to test the limits of Henry's patience. Read More...