Dwale

Beneath and around the clumps of ragged moss-grown elder and hoary stunted whitethorn (...) rise thickets of tall nettles and rank hemlock, concealing the deadly but alluring dwale —

All parts of the dwale are poisonous, said to resemble snake bite, but the roots are said to be four or five times as virulent as the rest of the plant.

It was not bog myrtle at all, it was dwale.

Monkshood and dwale belong to Hecate, the moon goddess of the witches, and by their use are witches able to fly.

The authors studied the ingredients and method of administration to try to ascertain whether dwale was effective, and they found it certainly could have worked.

'That is all?' Payne askes. 'You need no salve? No dwale?'

Dwale was a solution of wine mixed with a number of other ingredients, Some were pretty mile, like lettuce and boar bile. But the recipe also called for hemlock and belladonna, both known to be highly poisonous.

Cadell agrees the vial contains arsenic, not willow bark, and it is no wonder Rollo found relief from what was in the flask since it isn't wine but dwale.