Drops from Chloris in Abyssea - Tahrongi. Veinous Hecteyelid, Torn Bat Wing, Gory Scorpion Claw, and Mossy Adamantoise Shell are needed to pop it (NOTE: These are all key items, to obtain the key item, you must be the person to pull/pop the NM; It is -not- 100%)
As of July 2010 the Teiwaz is upgraded to a new weapon, Surya's Staff which is augmented through Trial of the Magians quests and gives 17% Cure Potency.