I'm trying to find information on Spellguards - exactly who are they, what they do and how you become one. Having just discovered FR maybe I'm not looking in the right places. Can anyone help me out here?
Ý think you are referring to Þpellguards of Silverymoon.They are guardians of the Mythal of the city and keepers of the arcane rules and laws.there is an academy of arcane arts in the city and you have study there or prove yourself to the archmage of Spellguards to join. Ýf you are looking for detailed info look to the silver marches and Silverymoon guide.Letter is unofficial i guess.
You could, in addition to the 3E source Silver Marches, also consult a couple of 2E sources. Volo's Guide to the North and The North boxed set both cover Silverymoon, as well, and both are available for free on the Wizards downloads page.