Best strategy for me has been to play as the Vampire and upgrade drain blood to 20%. Then upgrade the skill that lowers the enemy attack. Then leave your attack low (2 or 3), until you get to the enemy that can heal itself and you will never kill it. You will end up gaining hit points every fight as the enemy will end up with an attack of 1 or 0 (either starting with it or getting lowered from your skill) and every attack you have a 20% chance of gaining 8 or more hit points. So lose 5 HP to gain 8 or more.
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 "Dungelot"){kind=icon}
I will talk to Greg for this :)