Mages

While there is a Mage: Dark Ages book we'll be using the normal M20 rules where it concerns sphere magick. While the spheres are not used by magick users in the modern sense they function fine as a game system. The Dark Ages book should be used for guidelines of what is appropriate magick, what spells are typical, what foci would be used by a respective mage and for understanding what organisations there were at the time. It should be noted the Dark Ages book is set a little later than our campaign but much of what is said in there applies. However the Old Faith and Spirit Talkers would still be tribally ivided and only now are starting to understand that forming a united front may be the only way to save their traditions. Magick in this era is steeped in cultural and traditional divides. Priests of the old faith would not summon angels and messianic voices would consider bloodsacrifices an abomination in the eyes of the Lord. The different faiths regularly clash over idealogical differences. These differences are not considered philosophical as they might be to mages in modern days but rather metaphysical.
Another reason for using the standard M20 rules is that at some point we might want to fast forward a couple centuries and changing all the rotes to reflect the later used spheres would be an exercise in pointlessness.

Obviously not all modern abilities, backgrounds, merits and flaws are applicable for the setting. We use the Dark ages book where applicable.

Other Supernaturals

While this is primarily a Mage campaign if you have a good background story that fits in with the rest of the group I might allow it.

Changelings: The old faiths and spirit talkers respect the Fae. Not so much for the other groups. Hermetic mages often plunder freeholds for quintessence, the Messianic Voices consider them wicked spirits and the Vaeldermen consider them mischievous spirits best avoided.
shapeshifters: While the old faith, spirit talkers and Vaeldermen may have a grudging respect for shapeshifters most mages will hunt them down as monsters. This goes double for the Messianic Voices who consider werewolves demons in league with satan.
Bygones: In this era bygones are still roaming the lands in a wide variety of forms and have not yet been banished to the status of fables. Should you decide (and be allowed) to play a bygone remember that we may at some point make a leap into he future, which may leave your bygone character in dire straights as a new paradigm asserts itself with deadly results. Remember also that christians fear and even hunt many bygones.
Vampires: Vampires are currently not allowed as player characters. They are considered monsters by almost all mages and are not active by day when most other characters would be. Ghouls might be allowed.
Wraiths: with Rome's power crumbling in the british isles so does the Hierarchy's iron grip. Many an abandoned roman city is falling to renegade hands or worse, becoming true ghost towns best avoided. Given the separation between the Shadowlands and the living world wraiths are not allowed as player characters.