The Fool (spoilers for all RotE books, including LST)

[Farseer]

[But who will the next catalyst be, now that Fitz has retired?

I'm not sure he can retire as a Catalyst. ...Perhaps Fitz remains as such so that he can play an important role in future books, or maybe I'm just wishing.
[/quote]

There seems to me to be spoilers all over BUT just in case...*spoilers for Farseer/Tawny Man*

WARNING! CONTAINS HIGH LEVELS OF ELFBARK

Fool firmly states at the end of FF that Fitz is the Catalyst still and this is the main reason why he chooses to leave. He and Pilkrop had spoken about it and Pilkrop had convinced Fool that, if he remained in Fitz's life, he would alter Fitz's actions (even by some small change). This, in turn, could then possibly cause great harm due to Fitz's continued role as Changer. He IS the Catalyst and IS Changer.

It is interesting to note that even by Fitz's return to Aslevjal, Fool's presence in his life caused a huge change...if it were not for Fool convalescing there during his 'changing time' (as well as still recovering from his 'death'), and Fitz's subsequent revisit, Fitz would never have been absent for the month after he went to return to Buckkeep via the Skill Pillar...