What you know bout' Druids?

[Σ]

In The Annals of Imperial Rome Tacitus describes the slaughter of some druids:

On the shore stood the opposing army with its dense array of armed warriors, while between the ranks dashed women, in black attire like the Furies, with hair dishevelled, waving brands. All around, the Druids, lifting up their hands to heaven, and pouring forth dreadful imprecations, scared our soldiers by the unfamiliar sight, so that, as if their limbs were paralysed, they stood motionless, and exposed to wounds. Then urged by their general's appeals and mutual encouragements not to quail before a troop of frenzied women, they bore the standards onwards, smote down all resistance, and wrapped the foe in the flames of his own brands. A force was next set over the conquered, and their groves, devoted to inhuman superstitions, were destroyed. They deemed it indeed a duty to cover their altars with the blood of captives and to consult their deities through human entrails.

Also The Colloquy of Two Sages is actually a very enlightening dialogue between two Druid sages from way back in the day. They are very wise and one of the sages fortells of a future that sounds very much like ours. If you want to read it the text is here.

Does anyone on here know much about druid spirituality? I would be interested especially on information regarding the spiritual aspect as this is the religion subforum. Were they theistic or more akin to daoists? Any destricptions of their practice (meditations, rituals, ceremonial etc..) are also very welcome.

TL/DR
Druids bitch

[starvingniglet]

All I know is, I played a druid once in AD&D, and I had a juvenile moose animal follower, and I insisted on sleeping beneath conifers. 

[Zanick]

There isn't much known about them, that we can verify. They were a very private bunch. Much of the Druid revival in the last hundred years is either speculative or simply New Age garble. Caesar's account of his conquest of Gaul contains some information, though largely through a Roman lens. However, the absence of written records suggests they may have had other means of preserving their tradition--perhaps some long-forgotten memorization technique.