Several people seem to think that this post was one of my better ideas. I thought maybe I should follow my own advice. These answers are intended for players looting the Caves of Myrddin.
1.What is the deal with my cleric's religion?
You're probably a medieval Catholic type Christian who is theoretically answerable to some bishop. A Jewish cleric would work as well. Or you can play a Satanic anti-cleric. I could write more on this later and probably will.
2.Where can we go to buy standard equipment?
Enough adventurers are visiting the Caves that the stuff on the chargen price list is generally available, but you're also remote enough that the DM may roll d6 to see how many days it takes you to get completely supplied. Merchants come through here, but not everything is available the day you want to purchase it.
3.Where can we go to get platemail custom fitted for this monster I just befriended?
No dice. Platemail hasn't been invented yet. Chainmail custom made for a monster will probably require you to travel to Exonbury, some 90 miles to the east across some pretty treacherous countryside.
4.Who is the mightiest wizard in the land?
Didymus Ashlar, the Wizard of Wessex. By all reports he spends most of his time in the southwest corner of the map, well away from Cornwall. But occasionally he shows up in the area of the Caves of Myrddin, presumably searching for for the same magical secrets that draw so many PC magic-users.
5.Who is the greatest warrior in the land?
King Stephen is well known for personally kicking a good deal of ass. Two supporters of Empress Maude are also held in high esteem as fighters: her half-brother Robert, Earl of Gowan and the so-called Scourge of the West, William de Mohun. But some people dismiss Robert of Gowan's personal prowess and attribute his success in combat to his magic sword Morglaien, which once belonged to the legendary Sir Tristan.
6.Who is the richest person in the land?
Henry of Blois, brother of King Stephen and a powerful Bishop. That cat is loaded. Chera of Wintoncester, a Jewish moneylender, is also noted for her wealth.
7.Where can we go to get some magical healing?
There are no inns in the vicinity of the Caves of Myrddin. Most adventurers stay in an outbuilding on the grounds of the nearby Abbey of St. Emmet. A few of the brothers are Clerics of level 2 or higher. Cure Light Wounds and other first level cleric spells are generally available for a 'donation' of 250gp.
8.Where can we go to get cures for the following conditions: poison, disease, curse, level drain, lycanthropy, polymorph, alignment change, death, undeath?
The Abbott can personally cure some of these things, with 'donations' of up to 1,000gp. Harder cases will be referred to the Bishop of Cornwall, whose seat is about 60 miles to the southeast.
9.Is there a magic guild my MU belongs to or that I can join in order to get more spells?
The Invisible College of Thaumaturgy is a secret sixth college of the University of Christminster and serves as the closest thing to a Magic Guild in the setting. Any MU that starts play knowing Latin can consider themselves a student of the Invisible College. N.B. the journey from the Cornwall to Christminster is not trivial. The route stretches across much of the campaign map.
10.Where can I find an alchemist, sage or other expert NPC?
Possibly in Exonbury, previously mentioned. There are definitely sagacious and alchemical types at the University of Christminster. Abelard of Sulis is the foremost sage of the realm. Sulis is over 200 miles away, though closer than Christminster.