Liliths on Reefs Island are worth 1000 XP per, and usually drop some pretty good stuff. Of course, each can do ~50 points per hit.
Cyclopses are another favorite of mine, especially on the Cyclopses Coast Tunnel Enterance Screen. If my health gets too low, I can take the tunnel to the Witch's Finger, and use my tent. Cyclopses can also lead to a decent profit, as they can drop some good stuff. Again, Cyclopses can do ~50 points pet hint, and each is worth 600XP.
When I think my character is potent enough, I go after Minotaurs (and the odd Sea Giant) near the South Coast Tunnel Enterance.
The Cave 1 Square North of Fantrima yields lots of experience, plus some good stuff (especially the first time through).
Lit Nerd
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"O For a Muse of Fire, that would ascend
The brightest Heauen of Inuention:
A Kingdome for a Stage, Princes to Act,
And Monarchs to behold the swelling Scene." Henry V