I don't have a copy as yet ,
but the write-up is definitely appealing.
Can i use any of the Complete (Arcane , Divine , etc) series?
Splat books like Book of Vile Darkness and Exalted Deeds?
Races of ... series?
I realize the Cosmology is different.
Was thinking of Core Classes and Prestige Classes mostly.
What about Shifters , Changelings and Warforged from Eberron?
Don't want to change the whole look and feel of the background ,
more considering what my players might ask for ,
and possible integration.
Shifters and changelings would be entirely appropriate, given the existence of fey creatures in the game world. I could see adding warforged to the campaign as the product of natural philosophy experiments!
As for other core and prestige classes, New World Adventures talks about which ones are most appropriate, and presents seven new core classes and nine new prestige classes. Barbarians, fighters, monks, rangers, and rogues are the core classes explicitly excluded from NC, but some of the new core classes cover similar ground.
I think ED and VD are a bit high-powered for NC, but individual feats from those books could be added with care.
I think the Complete books could be good. Stormwreck and Frostburn would be cool.
I don't have the Nyambe book but I added the Witch class from the Witch book by Green Ronin. The Bastion Press fey book would be good for a Uropa game in Ireland or England. Someone mentioned that Corsair .pdf.
There's a steampunk book too by Fantasy Flight Games.
Nyambe is highly recommended.
I'm not familiar with the Green Ronin witch class.
Any steampunk material is of course great for natural philosopher invention inspirations, as long as the tech doesn't feel too Victorian. Maybe call it clockpunk?
The Green Ronin Witch class is similar to the one in the NC book but I thought it handled my idea of a alignment neutral witch a little better
I have their Shaman and Assassin class books too and think they're well balanced.
I've been finding some good Dragon articles too that would fit well with NC. There was an article about a year ago with "DR based" protective/weapon charm type items in it. So you could make anti fey cold iron ani-fey charms or garlic charm items that affect vampires.
Well the Witch in NC isn't alignment specific too much... The only thing is is that the witch gets her power from an evil outsider...But It doesnt mean the witch is evil.... It makes for a great contention of wills ...
Atlas Games' own Dynasties and Demagogues is a great resource for Northern Crown campaigns that involve politics, diplomacy, or intrigue. I would have included lots of feats and other info from that book in NC if space had not been an issue.
BTW, the Goodman Games Dungeon Crawl Classic "Bloody Jack's Gold" is easily adapted to Northern Crown -- a typical lost Aztec temple adventure, but lots of fun.