The Mysterious Murkshades in Swamp Romp, and possibly other places I haven't been to yet, are very confusing when it comes to attacking them. They have:
No Exp - Works correctly, but it shows an XP gain is incoming on my XP bar when mouse over occurs.
Mana Burn - I did not get afflicted with Mana Burn (I was a Thief, Taurog Worshipper, with a useless Viper Ward).
Magic Resist 100% - I didn't test this.
First Strike - I assume this applies the Mana Burn, but it's confusing when no Mana Burn takes place.
Bloodless - I assume this has to do with the Bloodmage or something.
So some things are a bit confusing right now.