Why, The Za! Court of course!
I beg your pardon? Five courts of Fae? 1) Winter, 2) Summer and...? "Billy" suggests an Autumn Court, now defunct, in YS on pg.75, so you might theorize about a Spring Court as well. But other than that, what would you count?
The 'court' of the Erlking? While he himself is a major player, his court has no powers such Winter or Summer (i.e. imbalancing the weather/climate, or some such). I am really, really curious which others you are referring to!
Wyld (the Erlking), (click to show/hide)the Fomor, and (click to show/hide)the Tylwyth Teg.
Wasn't trying to rank them, just enumerate them. That said, the implications around the TT might put them on par with the Summer and Winter courts. What I'm really interested in is how people may have used other courts...