Dragon's Blood
So powerful is this creature that the blood burns as if aflame. Precise measurements of this are wise, for too much and the magic will go dangerously awry.
Originally appeared in Ultima VIII: Pagan as a Thaumaturgy reagent, it was to have been used in Ultima Online as a reagent for the (originally canceled) Necromancy system.
On most shards it is now (was? before SA?) a rare item, part of a set commonly called Pagan Reagents.
With Stygian Abyss release, Dragon's Blood is now a common item from skinning any reptilian creature. It is used as a Mysticism reagent and certain quests in Termur such as Ortlem's "A Mystic's Journey" quest. I am not sure if the exact same graphic as the original Thaumaturgy/Pagan reagent or if there are now two distinct items.