The most important anathemas are in the canons of the first three ecumenical councils, especially the first two, and the canons of the Second Council of Nicaea (except for the reference to Chalcedon). Also important are the fifth and sixth ecumenical councils. Chalcedon itself is acceptable provided one denotes that the Oriental Orthodox are not monophysites, and their faith does not contradict that of Chalcedon, since the tenets for both churches in describing the relationship between the divinity and humanity of Christ are that there is no confusion, no commingling, no separation and no division.*
*For this reason, as I believe my friends
@dzheremi and
@Pavel Mosko would agree, I think Pope Dioscorus was unfairly deposed. Also the Oriental Orthodox anathematize Eutyches, who lied to Pope Dioscorus and was the founder of the true Monophysites, who by the time of their most well known philosopher John Philoponus in the 6th century, had descended into tritheism.
And of course it goes without saying that the main tritheist heretical sect today is Mormonism. I have heard reports from Syriac Orthodox and Assyrian clergy and laity that Mormon missionaries have really tried hard to prey upon the members of their churches. In the case of the Assyrian Church of the East I once caught two ethnic Assyrians who had been sent to attend tne divine liturgy or mass, called
raza, meaning mystery, by the Assyrians.