I found a website reviewing the Eastern Orthodox beliefs on Purgatory. The first part is about a kind-of lengthy debate between Latin and Orthodox Christians, you can read if you desire, but I'm just going to post the second half.
The Orthodox teaching on the state of souls after death is one that is often not fully understood, even by Orthodox Christians themselves; and the comparatively late Latin teaching of "purgatory" has caused further confusion in people's minds. The Orthodox doctrine itself, however, is not at all ambiguous or imprecise. Perhaps the most concise Orthodox exposition of it is to be found in the writings of St. Mark of Ephesus at the Council of Florence in 1439, composed precisely in order to answer the Latin teaching on "purgatory." These writings are especially valuable to us in that coming as they do from the last of the Byzantine Fathers, before the modern era with all its theological confusions, they both point us to the sources of the Orthodox doctrine and instruct us how to approach and understand these sources. These sources are: Scripture, Patristic homilies, church services, Lives of Saints, and certain revelations and visions of life after death, such as those contained in Book IV of the Dialogues of St. Gregory the Great.
Today's academic theologians tend to mistrust the latter two or three kinds of sources, which is why they are often uneasy when speaking on this subject and sometimes prefer to keep an "agnostic reticence" with regard to it (Timothy Ware, The Orthodox Church, p. 259). St. Marks writings, on the other hand, show us how much "at home" with these sources genuine Orthodox theologians are; those who are "uncomfortable" with them perhaps reveal thereby an unsuspected infection with modern unbelief.
Of St. Mark's four replies on purgatory composed at the Council of Florence, the First Homily contains the most concise account of the Orthodox doctrine as against the Latin errors, and it is chiefly from it that this translation has been compiled. The other replies contain mostly illustrative material for the points discussed here, as well as answers to more specific Latin arguments.
The "Latin Chapter" to which St. Mark replies are those written by Julian Cardinal Cesarini (Russian translation in Pogodin, pp. 50-57), giving the Latin teaching, defined at the earlier "Union" Council of Lyons (1270), on the state of souls after death. This teaching strikes the Orthodox reader (as indeed it struck St. Mark) as one of an entirely too "literalistic" and "legalistic" character. The Latins by this time had come to regard heaven and hell as somehow "finished" and "absolute," and those in them as already possessing the fullness of the state they will have after the Last Judgment; thus, there is no need to pray for those in heaven (whose lot is already perfect) or those in hell (for they can never be delivered or cleansed from sin). But since many of the faithful die in a "middle" state—not perfect enough for heaven, but not evil enough for hell—the logic of the Latin arguments required a third place of cleansing (''purgatory"), where even those whose sins had already been forgiven had to be punished or give "satisfaction" for their sins before being sufficiently cleansed to enter heaven. These legalistic arguments of a purely human "justice" (which actually deny God's supreme goodness and love of mankind) the Latins proceeded to support by literalistic interpretations of certain Patristic texts and various visions; almost all of these interpretations are quite contrived and arbitrary, because not even the ancient Latin Fathers spoke of such a place as "purgatory," but only of the "cleansing" from sins after death, which some of them referred to (probably allegorically) as by "fire."
In the Orthodox doctrine, on the other hand, which St. Mark teaches, the faithful who have died with small sins unconfessed, or who have not brought forth fruits of repentance for sins they have confessed, are cleansed of these sins either in the trial of death itself with its fear, or after death, when they are confined (but not permanently) in hell, by the prayers and Liturgies of the Church and good deeds performed for them by the faithful. Even sinners destined for eternal torment can be given a certain relief from their torment in hell by these means also. There is no fire tormenting sinners now, however, either in hell (for the eternal fire will begin to torment them only after the Last Judgment), or much less in any third place like "purgatory"; all visions of fire which are seen by men are as it were images or prophecies of what will be in the future age. All forgiveness of sins after death comes solely from the goodness of God, which extends even to those in hell, with the cooperation of the prayers of men, and no "payment" or "satisfaction" is due for sins which have been forgiven.
It should be noted that St. Mark's writings concern primarily the specific point of the state of souls after death, and barely touch on the history of the events that occur to the soul immediately after death. On the latter point there is an abundant Orthodox literature, but this point was not under discussion at Florence.
