The song of the Earth - Caiseal Mr

Nine seasons have passed since the Druid Council of Eirinn banished the sadistic Christian, Palladius, from its island shores.
But now an even greater force has arrived from Rome in the shape of Patricius, a powerful and fearless bishop who is determined to corrupt the ancient traditions of the Druids to his own ends. Aiding him in his task is a monk whose very name inspires fear and hatred in all Eirinn.
It is nine seasons, too, since Mawn and Sianan began their Druid traning. Now they face their greatest test: a journey to the Otherworld. Only if they survive can they partake of the Quicken potion brewed by the Faery kind, which will make them Wanderers, keepers of the ancient magical ways.
But as they undergo their testing a fierce confrontation is taking place between Patricius and the High-King of Eirinn. Neither leader wishes for bloodshed but there is one amongst them who is determined to destroy any hope of peace, intent only on violent and bloody revenge.