I think that setting a saga slightly before the Fourth Crusade and the Fall of Constantinople would be interesting because it would let you play through the events and help determine their outcomes, or at least how the Order is affected in the aftermath.
Let's go to hard antiquity and play Ancient Egypt's priests with gods culte instead of houses. Pick the hyksos era and let's call it ars aegyptica.
It strongly depends on where are you setting your Saga and how spicy is the mix between historic events and Hermetic history timeline, if applicable.
For example our saga is placed in the Isle of Man, and 1220 is a pretty fitting year to play there. From the historical We have a pretty interesting mix of gaelic peasants and norse rulers, a lot of civil wars, revolts, and political maneuvering; from 1225 to 1226 there will be a civil war of, the king will have his brother Godred Dunn killed in 1236 and dies in 1237, and in 1248 one of Dunn's sons will kill the new crowned King Reginald II while his brother claims the throne, which will start a cil war that will last until 1252 (a lot of years of war in an island so small that you can cross it in one day from side to side!), all mixed with the increasing influence of the Dominion, which 1260 being a very interesting year because there is a prophecy saying that Armaggedon will arrive 1260 years afer the birth of Christ... and in the Mythic landscape the norse dudes are expected to have their wizards (hello, Order of Odin!) and the island has a long history of hermetic tragedies; in 866 the Covenant of Rector Maris was founded in the island and destroyed within 6 months, in 938 another attemt was made to establish a covenant there, Rector Novus, and was destroyed within a year, but only 6 years later Diedne founded the Caarjyn Arawn covenant, which managed to survive and prosper (well, until the Schism War, when it was destroyed anyway), and there was a last attemt to settle magi there in 1160, founding the Servus Maris covenant, which was destroyed again in 6 months (that makes a lot of hermetic ruins to explore), and a letter was sent to Loch Leglean's tribunal, saying something like "don't ever try to come back", which was confusing, because Man have three big dragons, one of them deeply hating magi and suspect of being friend of the diedne magi back in the day, but it doesn't seem like the kind of enemy who writes threatening letters... and on the top of that the island is claimed by both the Loch Leglean and Hibernian tribunals, but the issue was relatively calm as after all there weren't any magi there, but if our characters manage to settle there and survive whatever destroyed the former establised covenants there, a storm of inter-Tribunal proportions will start around the island, asking it to decide for a tribunal, being claimed by both, and so on. And then there are the fae, of course, with Man himself, being a faerie king that pretty much actually owns the island.
So I think the trick is picking a place, and then reading the hermetic timeline for events happening there and doing a quick search on wikipedia for historical events, and then place your saga in the right time and place that ensures a lot of ideas for stories. A lot of interesting stuff happened in a lot of places at different times; if you dig long enough the real problem will be with possible settings and times to discard.
I would have never thought that such a small island would have so much going on.
This isn't the first I've heard of it over the internet, and my brother ran a game on the Isle of Man with his friends for two years. Seems to be a good location.
That could be exceedingly interesting, especially if you add in the Greeks and other nations with various magical traditions.
Eras I have contemplated playing Ars in:
Ancient Babylon - play out your "tower of babel" fantasies as you build an epic temple, dealing with the airy spirits and avoiding the plagues of Nergal. As the empire conquers foreign lands, help with taming those pesky foreign gods (as the Babylonians steal people's idols, are they taking arcane connections to a people's magics or taking the item needed to summon an Aspect of a Daimon?)
Ancient Rome - best times I feel are:
60ish AD, begin with Nero's reign and then have the madness of The Year of Four Emperors in 69 throw their world upside down. As rebellion hits the Empire, do you go raid Judea (chance to steal the Ark of the Covenant and the treasures of the temple) or join in with subduing Britannia (a favourite of mine as then you get to see the founding of Eboracum in 71 AD)?
161 AD - Marcus Aurelius becomes Emperor, there are wars with Parthia and Germanic tribes (a chance to have mages of Mercury slaughter their enemies at future sites of the Rhine Tribunal) . There are also horrific plagues (the Aurelian plague is probably smallpox hitting Europe for the first time) , and the legendary Galen is the imperial doctor. It is also the age of charlatans - Lucian mocks the snake god Glycon in all his puppety ways - is his high priest a total fraud creating fake wards against disease and using a puppet as an idol, or is the priest an infernalist spreading disease, and the icon of Glycon depends on the priest's Finesse skill to impress others? This is followed by Commodus in all his vanity and insanity, with priesthoods doled out to favourites, months renamed, priestesses forced to perform their rites until they lose an arm, and his eventual murder. You then get the piece de resistance - the year of the five emperors where the first replacement for Commodus tries to make reforms and gets murdered by the Praetorian Guard, there is then an auction for the Imperial throne won by a wealthy man who then has to devalue the currency to pay for it all, followed by civil war as three rival Generals (Severus in Pannonia, Clodius in Britannia and Phillipus in Syria) all claim the throne. If you take the Historia Augusta as being true and accurate, you have all kinds of gossipy details about the emperors and their magical and religious practices to use.
1480s to early 1500s - as the printing press works its magic, steel technology allows plate armour and advances in navigation open up the Atlantic in the 1490s, the question is do you start early to allow players to build power just before the great voyages of discovery, or start a bit later - 1517 and Martin Luther kicks off the reformation, for everyone wanting Church/Divine plots.
I'd play in this setting!
Just a couple of brief notes:
For those interested in an Isle of Man saga, Hermes Portal did a two-part exhaustive sourcebook for Isle of Man sagas in issues 14 and 15.
For other dates to start your saga, I'll just add that 1187 was the starting date in earlier editions of Ars Magica.
Ars Magica, the Civilization edition. Start in 4000BCE or soon after Creation or the Flood, as you prefer. Don't worry about LRs other than 'you must have one'; let Warping and hazards do their thing. Each season starts off being 20 years long. When Jesus is born and at the millennium, wave hands and shorten this, should your magi live so long. Can you build a Covenant to Stand the Test of Time?
790 AD, or any point in the 9th century in Brtain.
Aelfred and successors and the Danes... -->lots of turmoil, Viking feel rather then middle ages as we know them
19th century: Victorian magic
I'm very happy with my 790 aD Germany setting: https://forum.atlas-games.com/t/domus-parva-790-a-d-alternate-setting/10246/1
Works great with Fimbulwinter and Twilight of the Gods from Dies Irae.
I also think a date within the Carolingian era is ideal for an Ars Magica game. It provides a wilder, emptier, and generally less sedate Europe than the baseline setting, while maintaining the general Medieval context.
I'd love a version of the game set sometime in antiquity but it would take a good deal of work and adaptation to even approach the level of accuracy and detail of medieval Ars.
It also allows to keep all the basics of the Order of Hermes, its founders and Houses, and of Hermetic Magic - while doing away with some later complexities like the Schism War or MuVi rules and errata.
AFAICS it might appeal to many troupes.
I am working on an Ars 1520. Some of the setting is based on Mark Shirley's Sub Rosa #16 article on Ars 1470. Most of it is breaking from standard Ars of Mythical Europe and developing firearms and new magic breakthroughs ( like what can the Magi do with clocks). I think it is an interesting time for all the reasons you listed.
What can Magi do with clocks? Inquiring minds want to know. 8)
Let's face it: You don't need clock magic to do faerie magic, but if you want to be a Faerie Godmother, there's no substitute for having a spell end when the clock strikes 12.
That is part of it. At this time many towns are starting to get clock towers. It is a matter of civic pride to have one. So urban magi would be able to use some of the new durations like hour or stroke of . Keying magic to stop at the bell's tolling. But no clock tower/ large clock then no new durations to use. Can't have a magi casting a spell that lasts until a bell tolls on a person far in the country. Just not very balanced.
The durations don't depend on the bell or the clock, just on the kind of time measured by the new kind of clock, with hours of constant duration, etc.
But one could also have a new kind of Target, to use a specific clock to define your notion of time, which of course would create new issues. Still, that's the way to cast a powerful ritual, such as It's Morning in America...
I found my old note written down on Ars settings that I'd hidden in a notebook, this is what I scribbled a few years back:
Ancient Babylon - tower of Babel, priests of Nergal, Airy Powers, foreign Gods
Ancient Greece - ancient Minoans threatened by a volcanic explosion, or the classic period with well-educated Athenians fighting off threats?
Rome - years of many emperors, plagues, many religions and gods to use.
Arthurian times for a British Isles setting, and be "Rivals to Merlin" or "Apprentices to Merlin" rather than heirs.
Rise of Islam - Arab conquests are under way in the century and a half before the foundation of the Order of Hermes, so here's a chance to see what's left of the Roman world getting pushed out of North Africa and the Levant in a time when Mercurian magic is weakened.
14th century - the great famine 1314-17 and black death make for apocalyptic games and extreme suffering in contrast to the 12th & 13th centuries of most Ars.
1490s - printing press in full use, voyages of discovery, plate armour, Pope Alexander VI
I probably should have written this down more clearly at the time.
I think this game is called "Pendragon". Though the magic system is ... er ... not as thorough as that of Ars Magica, admittedly.
EDIT: Though you could probably grab the Pendragon Grand Campaign and have an excellent saga outline I suspect