Just to bend the nature of the thread before it's even really begun, here's a list of "events" I started pulling together, based on published books of different editions, for reasons that will unfortunately forever now be nameless.
I should point out that as far as we know, Boudicca was never actually a druidic priestess. Except in my world... That should be a clue that not all events listed are official. Some have been added (it's like a game; you have to work out which ones are official and which aren't).
Divitiacus, magistrate of the Aedui visits Rome to request military aid against his enemies.
The Romans destroy a Druidic enclave on the island of Anglesey, also known as Ynys Mon
Boudicca, Druidic priestess of the Iceni, leads her army against the Romans. 80000 Britons die in the conflict and Boudicca slays herself with poison.
Saint Columba defeats the Druids at the Battle of Culdremne.
The First Tribunal of the Order of Hermes
Damhan Allaid slays his Druidic tutor and steals away with his secrets.
Pralix comes to Stonehenge and Loch Leglean
The Diedne in the Rhine united in a show of political force, choosing to become a power in the Tribunal. They were known as the Rowan Gild.
The covenant of Ungulus was founded in the Stonehenge Tribunal by prescient Flambeau somehow expecting animosity with House Diedne to spill over.
The covenant of Lumen was founded in the Stonehenge Tribunal.
The covenant of was Lumen destroyed in a surprise attack by Diedne magi
The Flambeau and Tremere magi of the Rhine Tribunal led a purge of the Rhine Diedne. All members of the Rowan Gild were exiled and Wizard War declared against them. Though their covenants fell many of the Diedne managed to flee the Tribunal with their lives. Magi from other Houses who had joined the Diedne in the Rowan Gild were not spared.
In order to carve out a protective barrier, House Diedne orchestrated a cull of Gruaguchan hedge wizards around key druidic sites in the Loch Leglean Tribunal.
The Schism War reached Loch Leglean with the loss of the Diedne covenants Holy Oak, The Well of the Head, and Druids’ Dale.
These three covenants were attacked by a core force of Tremere and Flambeau aided by several other Scottish covenants and a number of native hedge wizards, the Gruaguchan.
House Tremere declares what everyone else only whispered about, open war on House Diedne. Houses Flambeau and Jerbiton follow.
A Grand Tribunal is called and held at Magvillus in the Roman Tribunal. House Diedne is renounced and all magi declared “Orbisâ€.
The Nameless Covenant, Domus Magnus of House Diedne, is destroyed in the last official action of the law.