Shrink is a very powerful spell.  Most of the battles against the most powerful monsters, slags, dragons, etc., become trivial when they are shrunk.

Maybe depending on the size of the monster will determine how much it is shrunk; e.g.  a cave bear can be shrunk 50%; an orge or troll can be shrunk 30% as well as it's attack; a slag maybe 20% and loses that much; drakes or dragons shrunk 10% and loses only 10% of it's attack.

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Champion spear gives +2 attack per level of wielder.  Maybe a cap or +1.5 attack per level instead.  Otherwise the champion becomes too powerful.