The third Relic needed to thwart the Grey God's watch towers is the Lay of Victory, a songspell sung by the late Ossian, Bard-Protector of the Tuatha de Danaan. If the party raises Ossian's essence from his Torc, using the Cauldron, and they possess the Lay, then Ossian can reverse his spell - if - he is raised at the Altar of Skulls located at the heart of the Grey God's hidden underground temple. The Altar of Skulls is the power source for the watch towers which prevent any intrusion into the lands of the Shadowgaunts where a portal to the plane where the Grey God's avatar can be found.
If the party possesses the Torc and the Cauldron and they speak with Rowan about these matters, he will direct them to find Llywarch, who is the poor bard mesmerised at (63,84), by shouting his name he will snap out of his trance and be freed. He will join the party and ask them to find the first watch tower that the party should have discovered to the north through the blocked off canyon at (59,53). He will give up his life to destroy the watch tower enabling the party to enter the burial marrow (Cruaich Meor) at (64,42) beyond the tower wherein is located Ossian's tomb and his Lay. A Lay is a Bardic equivalent of a scroll.
Retrieve the Lay and bring it to Rowan. With all three of these Relics the party can raise Ossian at the Altar of Skulls, of course, they have to find it and discover the various keys to gain entrance.