The Island of Dr. Moreau
There's definitely a strong case for Moreau as Guide/Mentor. Hear us out and see what you think.
Okay, Moreau and Prendick are both biologists, and at first, Prendick doesn't see anything wrong with a little vivisection. He even says, "there was nothing so horrible in vivisection as to account for [Moreau's] secrecy" (7.17) But, as the novel progresses, Prendick does indeed see what is so horrible about Moreau's vivisection (and then some). Moreau eventually explains his desire to discover the laws of God through his experimenting on the flesh of animals, and Prendick is just flabbergasted by what he hears.
Fast forward to the novel's end. Prendick seeks solitude away from humanity, just like Moreau. And just like Moreau, Prendick's studies focus on discovering God's "vast and eternal laws of matter" (22.7). There is a difference though, and it's a big one. Whereas Moreau sought his laws through the evolutionary pain and suffering of animals, Prendick searches through chemistry and by looking toward the stars via astronomy.
So, Moreau sort of becomes Prendick's mentor. Through him, Prendick discovers the questions he desires to seek answers to. Prendick also learns from Moreau's mistakes and seeks those answers in more peaceful endeavors.
So, Moreau is kind of Prendick's mentor and antagonist all wrapped up in one. He guides Prendick by putting Prendick through hell. Is Prendick better off for it in the end?