Mat was lucky even before he went through the doorway. But he wasn't always a great general. The dagger from Shadar Logoth ate holes in his memory. So after he goes though one doorway and gets his questions answered, he goes through another, not realizing that the situation is different and he will have his demands met at a price. So his demands are this: 1. to be free of Aes Seadai 2. to have the holes in his memory filled 3. and to be out of the place the doorway led to. He forgot to name a price, so it was set for him. The fox people were wearing harnesses made of human flesh, so at least once price is likely death. So his demands are met. He is given the amulet that protects him from channeling, he recives thememories of hundreds of war leaders, and he is sent out of finn-land (I think if he had not made this demand he would have been killed or trapped there). I don't know what the spear is, but it must have had something to do with the price.