Editing 857 (section)

== Events ==
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=== By place ===

==== Byzantine Empire ====
* Emperor [[Michael III]], under the influence of his uncle [[Bardas]], banishes his mother [[Theodora (wife of Theophilos)|Theodora]] to the [[Sancaktar Hayrettin Mosque|Gastria Monastery]]. Bardas, the ''de facto'' [[regent]], becomes the most powerful person in the [[Byzantine Empire]].<ref name="Treadgold450-1">{{harvnb|Treadgold|1997|pp=450–451}}.</ref>

==== Europe ====
* [[November]] &ndash; [[Erispoe]], ruler ([[duke]]) of [[Kingdom of Brittany|Brittany]], is assassinated by his cousin [[Salomon, King of Brittany|Salomon]] and followers, in the church at [[Talensac]]. King [[Charles the Bald]] acknowledges Salomon as the rightful 'king' of Brittany.
* A Danish [[Vikings|Viking]] fleet raids the cities of [[Dorestad]], [[Paris]] and [[Orléans]]. Others sail up the [[Oise (river)|Oise River]], ravaging [[Beauvais]] and the [[abbey]] of [[Saint-Germer-de-Fly]] (approximate date).
* Viking chieftain [[Rorik of Dorestad|Rorik]], with the agreement of King [[Lothair II]], leaves Dorestad with a fleet and forces his rival [[Horik II]] to recognise him as ruler over [[Denmark]] (approximate date).

=== By topic ===
==== Medicine ====
* The first recorded major outbreak of [[ergotism]] kills thousands of people in the [[Rhine|Rhine Valley]]. They have eaten [[bread]] made from [[rye]] infected with the [[ergot]] fungus parasite ''[[Claviceps purpurea]]'' (approximate date).
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