The sorceress Sarah. People apparently call her 'the Great Sorcerer' or something.
Literal
Sorceress Sarah. People [topic-は] her [object-を] 'great-sorcerer' [or something-とか] call [apparently-らしい].
Fantasy-novel narration. 魔術師 'magician, sorcerer' and 大魔導師 'Great Sorcerer/Grand Magus' belong to a specialized fantasy vocabulary (導師 = 'teacher, guide' in Buddhist contexts, appropriated for fantasy 'high-level magic user'). The first sentence is a noun-ending fragment introducing the character. とか attached to a quoted name gives 'or something like that' — distanced hearsay. らしい marks the whole claim as reported/secondhand.