From the Town Cryer article.
"...in the wake of last years invasions by the Elemental Titans...those pagan zealots...."
Ultima 8 Pagan is going to be your lore source. U8 is also the Titan story arc.
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Tenebrae: Sorcery: http://wiki.ultimacodex.com/wiki/Tenebrae
"Tenebrae, the city of eternal twilight, is the only known city remaining in Pagan after the great war, situated on the island of Morgaelin."
Boreas: Theurgist: http://wiki.ultimacodex.com/wiki/Boreas
"Boreas was more than a healer of wounds and ills. Pagan seemed to gleam during her lifetime...buried grief that still burns raw for Boreas, wisest of the Theurgists"
Moriens: Necromancy: http://wiki.ultimacodex.com/wiki/Tomb_of_Moriens
"The Tomb of Moriens is the prominent central feature of the Cemetery of Pagan in Ultima VIII. As the name suggests, Moriens, the first Necromancer, is buried here..."
Carthax: Tempestry: http://wiki.ultimacodex.com/wiki/Carthax_Lake
"Carthax Lake is an underground body of water which lies beneath the Catacombs of Tenebrae, deep within the heart of Morgaelin. It houses the ancient temple of Hydros, the Titan of Water."
Titans: http://wiki.ultimacodex.com/wiki/Elemental_Titans_(Pagan)
Lithos: Moriens
Hydros: Carthax
Stratos: Boreas
Pyros: Tenebrae