Tears to Tiara II: Heir of the Overlord
The game draws heavily from Welsh, Celt, Christian and Roman mythology, with characters named Arawn, Arthur, Epona, Llŷr, Morgan, Pwyll, Rhiannon, and Taliesin. Set in a Late Antiquity-inspired fantasy setting, story starts on an island Erin (or Hibernia, as shown on an in-game map) on the west border of the Holy Empire.
Prologue is centered around the precognition-gifted priestess of the Gael tribe, Rhiannon. She is kidnapped by a rogue priest of the Holy Empire, Drwc, to be used as a sacrifice in a ritual meant to resurrect the Demon King Arawn and put Drwc in his favor. As a response the Gael people burn their village and swear to bring Rhiannon back or exact revenge on the Empire.