This is a series of poems apparently composed in the which mentions Artorius, and is an obscure predecessor of Geoffrey of Monmouth's even more fanciful "History of the Kings of Britain". To place it within the context of other Arthurian works:
Arthur is mentioned several times in the background as a war leader allied to the unnamed King of Caer Eidyn, who was contrasted by his victories in battle, compared to the King's troubles which make up the bulk of the epic.
The name "Zorlith" is one of two names used for the traitor within the King's court, the other being Adomnan. The two names appear inconsistently used, and not much is said of this figure's actions. It appears from the conclusion that he escaped, taking many of the men from the King's retinue with him.
The name "Anstaria" appears in a list of women who descend upon the warrior Camarthen and offer him hospitality during his return from a battle against the Saxons. He leaves apparently with some distaste for them, being intent upon his mission. It is ambiguous within the narrative where they are from, but there are parallels to the faerie elements of later stories.
The name "Thursif" appears solely within a curse which a mortally wounded Saxon leader casts upon the warrior Maelgwn. The full line is roughly "May the depths of the black Earth swallow you and your Sighle, and the fiery tongue of Thursif strike you".