Rune sticks
The Letter Sticks were "long rods of ash wood carved with spells" inscribed in "ancient symbols".
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Dallben would consult Hen Wen, the oracular white pig, through the use of the sticks, but only in a matter of greatest urgency. The great enchanter attempted to do so during the rise of the Horned King, but Hen escaped before Dallben could retrieve the rods; and once, successfully, later after Dyrnwyn had been stolen by Arawn.


Hen Wen2
The Letter Sticks were prophetic devices. Dallben would set them upright in the soil of Hen Wen's enclosure, and Hen -- if she were feeling unafraid -- would walk up to various rods in turn, while Dallben scribbled the meaning of each selection on a bit of parchment.
Hen might need gentle encouragement from an Assistant Pig-Keeper, assuming one was handy, to complete the prophecy, especially when the matter was one of perilous impact.

Instances of Use

The first time Dallben wished to use them, within Taran's seeing, was during the events of The Book of Three, but the enchanter could not find the rods in time. The only instance Taran ever saw of the Letter Sticks was at the outset of the events of The High King. In the latter episode, the rods exploded before Hen Wen could complete the final prophecy.

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