As a proper noun mentor
is (greek mythology) odysseus's trusted counselor he was assigned the responsibility to raise odysseus's son telemachus, while odysseus was away fighting in troy.
As an adjective mentorial is
of or relating to a mentor.
Other Comparisons: What's the difference?
To act as someone's mentor
Article on the etymology and history of the word “mentor” on languagehat.com
Of or relating to a mentor