In the 370s, a schism developed within the Circulan School of House Lem when half of the magi of the Circulan covenant Ambulator Caeruleus came to the conclusion that the founding of their covenant all the way back in the year 340 had been a mistake. The Books of Lem, they claimed, clearly indicated a different course for the Circulan movement at the “blue” stage of its development. In 379, therefore, these magi left Ambulator Caeruleus to rectify the error by founding a new blue covenant, Sol Caeruleus.
Beliefs about the naming and location of the “blue covenant” were not the only doctrinal differences supported by the Sol Caeruleans. They also advocated a somewhat laxer interpretation of Circulanism than that supported by the more orthodox Ambulator Caeruleans, likely in part out of a desire to compete more successfully with the new and rapidly-growing Imbrian School.
The dispute caused a good deal of bad feeling, not only because those who remained behind at Ambulator Caeruleus took umbrage at the suggestion that their covenant was itself an interpretive error, and not only because they felt that the Sol Caeruleans were proposing a “watered-down” version of Circulanism, but also because the Sol Caeruleans’ action was seen by many as a sign of Circulan weakness and divisiveness, which in turn helped to precipitate the steady usurpation of the Circulan Movement’s role as the leading sect of House Lem by the new Imbrian School. The magi of Ambulator Caeruleus held the Sol Caeruleans’ partly responsible for the overall decline of the Circulan School as a whole — and they resented them for it.
Particularly resentful were [L69], first filia of Ambulator Caerulean founder [L47b], and her descendants. In 392, after a series of ever-escalating disputes between the two groups of magi, [L69]’s first filia [L97] killed Comæ Crocæ Cruntæ, the filius of Sol Caerulean founder Glutinator Genitabilis. Glutinator swore vengeance and since then, these two Lemmite lines have been out for each others’ blood. In 410, Glutinator’s second filius, [L121], avenged his brother’s death by killing [L97]’s sister [L124], and now the Ambulator Caeruleans have vowed that they will not rest until her death has been avenged. So far, there has been no further bloodshed between the two lineages, but nobody is quite certain how long this state of affairs might last.
The feud has proved exceptionally divisive to the Circulan School as a whole, and it has served to transform what otherwise might have been a minor doctrinal dispute into more of an outright schism. In 421, when a group of magi from both Sol Caeruleus and Ambulator Caeruleus joined together to found the next covenant in the Circulan cycle, Vomer Purpureus, many hoped that this joint-endeavor would bring an end to the schismatics. In spite of the participation of the magi from Ambulator Caeruleus in its founding, however, [L69] and her students have refused to recognize the legitimacy of the new covenant, insisting that like Sol Caeruleus, it is nothing but an heretical off-shoot of The One True Circulanism, to which they now claim to be the Order’s last remaining adherents.

Note on the Blue Feud
No, really. That's all the detail that exists on this thing. It's not even clear whether the Caeruleans have been offing each other in formal duels, or through sneaky assassination, or through outright murder, or what. What you see is what there is.
Silly Lemmites Schisms' are for Menareans
Ah the Circulans. I see it more as sneaking about waiting til your target is out in an exposed, hopefully vulnerable position then walking up, issuing your challenge and blasting them away. It's not something you can do very formally because there are members of both covenants who would rather there not being a mage feud.
These guys just aren't much longer for the Known World. As its been said, chances are some of these people may go off and join Quintus or the Purple Hand to get away from this blood feud.
Meta note on the schism.
“Sol Cæruleus” has a new connotation post-Firefly, don’t it.
Oh Kip...
You got any vested interest in this feud? If not I have some ideas that are percolating.
Really if anyone has any interest let me know.
Nothing vested.
Percolate away!