OK, what is the deal with the Champion's titles. "Regent of the third day and the fourth heaven" I can see, with the 7 days of creation/7 heavens thing. "Avenger of the Luminaries" I can see as him/her being the chief warrior Power. But "Winged like the Emerald?" "Providencer?" Are these from a myth, or did DD make them up?

That's a good question. Too bad I always miss DD's chats so I can't ask her. I'm rereading the series right now. I'm on "A Wizard Abroad" so I'm not quite there yet. Maybe you can get into her next chat and ask her.

"Winged like the Emerald" is probably a description of "their" (whatever alien species) perceptions of the Champion. Where Kit, Nita, and Dairine (Carmela? Nita's mother? I don't know about non-wizards — but it's probable that she saw that too) see a humanoid of sorts, I have a feeling that non-humanoids have their own glorified version. Whatever glorifications that means, I don't know. Probably "Winged like the Emerald" is a title showing his splendour. Like the "Finned/Winged Defender." By the way—where did you get those titles? Rashah (I mean the planet)?

"Providencer" — another call for the dictionary... While there is no regular word 'Providencer', it does seem to have roots in the word providence, or even just provide.
From http://dictionary.reference.com/search?r=2&q=providence :

1. (often initial capital letter) the foreseeing care and guidance of God or nature over the creatures of the earth.
2. (initial capital letter) God, esp. when conceived as omnisciently directing the universe and the affairs of humankind with wise benevolence.
3. a manifestation of divine care or direction.
4. provident or prudent management of resources; prudence.
5. foresight; provident care.

Now do you see? I think it makes sense now. "He who gives providence," or something like that. But Spyells is right, you might ask DD.

On the other hand... I have my own question about titles: It seems to me that the order of rank in YW is plain enough, at least from pre-Ordeal wizard up to Wizard up to Advisory up to Senior level. But what's the rest?

*doesn't remember these titles* i'm guessing, though, it's just titles people gave the champion, because in their mind it fit....different people tend to have different ideas, which would result in many titles, some of which wouldn't make sense to us..(i'm getting a slightly better undesrstanding from dorthiea's post, which is why i can answer at all)

Well Young Reader maybe you can explain it to me then. I guess over time different titles are given for what the One's Champion may have done for that civilization or people. But so far that's all I've got.
http://en.wikipedia.org/wiki/Titles

Have you had a look over at the errantry wiki? There are a couple of entries that refer to the One's Champion, and you can follow the line out to them from http://www.youngwizards.com/ErrantryWiki/index.php/One%27s_Champion%2C_the

I would hazard, though, that the One's Champion would have been given different names in different times, and different places (such as we know them - I seem recall that the Powers don't exist in the same time and space that we do, they more 'visit' it). This would make sense as each and every planet - with its different life-forms and cultures would have a different name for the One's Champion.

Its probably worth reading this page over at ErrantryWiki too, as it points out some of his more recent names on Earth.

if you go around to different places for CENTURIES, doing waht the powers do, you're BOUND to pick up more then your share of titles...every place, in every time will give you another one, and when you return to them a few centrueies later, they'll give you another title yet.