: "Of this Order the number is unknown; but of those that came to the North of Middle-Earth [ ... ] the chiefs were five."

: To my understanding this either means:

: a) that the only the masters of the Order came to ME while the majority of its members remained in Aman, or;
: b) that an unspecified number of Istari (one would suppose more than six) came to ME under that guidance of these five.

: Either way, 'therein lies a tale', so to speak.

: Any ideas?

: Cheers
: Berembrôg

Maybe there were only five but people thought there were more?

But if that's not the case, maybe the others went to help sentient beings on other continents, like South Endor and the Dark Continent (assuming anyone lived there; maybe the eastern Avari developed boats with the aid of Osse?).