The True Britannians
When Trammel was created, and Lord British began the mass exodus, there was many who wished to stay behind to defend Felucca side of Britannia. The True Britannians are the loyal force of Lord British, which wishes to establish his rule back on Felucca. This is no means easy job as they are forced to fight fellow Britannians as the Council of Mages has formed its own ranks to rebel against Lord British.

The Council of Mages
When Lord British and Nystul created Trammel facet without consulting the Council of Mages it broke a deeper grunge between the Court and the Council. The grunge was tried to be resolved with peaceful meetings so that the Court and Council would be one, once again. However the meetings were dissolved into dust because of the deep differences of opinion and the doubt cast by a stranger stating that Nystul had been warned of the dangers (collapse of nature) of the spell.

The council decided that Lord British had simply done wrong to Britannia and therefor he should not be the ruler of Britannia anymore, Felucca should be cured in hands of the Council, nothing else. And this lead eventually to involve Council of Mages and it's supporters to the war.

The Followers of Minax
To revenge her lover and mentor's death, Minax returned from another facet to the world we now know as Felucca. Her hatred was concentrated against Lord British for it was he, who set the stranger to kill Mondain. In her initial attack she gathered undead and hateful creatures of deepest dungeons to her ranks and assaulted the biggest towns of Britannia. After temporally gaining hold on Trinsic, she begun to recruit Britannians to her ranks. With promises of wealth, power and better rule she has made many men and women to swear allegiance to her. Now her forces are in full-scale war against Lord British and anyone who stands against her rule.

The Shadowlords
There is not much known about the Shadowlords. They are mystical order who seems to have it's own goals, yet unknown to us. However they seem to be familiar with necromantic arts and controlling the undead, even their base is at deepest corner of Yew crypts. It is also said that they worship beings called the Shadowlords, who they say possess the ultimate knowledge and power. The order of Shadowlords is generally considered to be full of lunatics and cultists, however they are considered very dangerous to mess with.