I have two suggestions:
1) Make the magic have a certain risk or fun factor, to add a bit of randomness. In this respect, magic can be similar to Ars Magica, an RP game. The spells would be medieval style, manipulating medieval ideals and physics. There would be no "create intense light that burns the retina" (since no one knew what a retina was in 1400ad), instead it would be more along the lines of "create bright light that scares away monsters".
No spell would be a mundane spell, and each spell could do significant damage (or whatever effect it does). However, there will always be a trade-off and an 'oops' factor. The trade-off is always there and it's effect on the caster is dependent on the power of the spell, sometimes being as benign as "Urist McCaster's hands are black and blistered" from casting too many fireballs. Healing spells would age the caster faster, puberty spells would cause the caster to grow more hair, tantrum fits with calming spells, etc.
Oops factor would be that slight chance that everything blows up in your face. It could be the spell just doesn't cast, the spell casts but has a negative effect, the spell fails and you think it's working (think fire walking spells), the spell hurts the caster, the spell does something completely random like spawns bloodthirsty rabbits, etc, etc. That way, even though spells are powerful, there is always that chance your healing spell will cause tiny green chest hairs to sprout all over the injured dwarf's split lip, suffocating him.
2) Make the magic system completely regent based, with only creatures, monsters and demons having access to magic in itself. The creatures would have to be captured and harvested of their "magic" organs by a shaman, then either grounded and mixed by an alchemist, imbued into weapons by an evoker or made by a moody dwarf into a floating bed.
The first thing you would have to do is locate a creature with a magic organ you want. Ex: a Medusa that can turn a dwarf into stone. You then have to capture or kill the creature to harvest the organ, without damaging the organ. You could then mix the regent with another substance or regent. Ex: mix a Medusa head with some adamantine thread, and the next thing that views the head turns into a wall of adamantine.
Using captured goblins and a series of trap mechanisms could also create creative gathering methods. Ex 2: Manticore shoots darts that instant kill dwarves. Manticore is locked in a small room with only one window to shoot out of. Use trap door to drop goblin prisoner right in front of the window. Manticore shoots goblin full of holes. Another trap door opens and drops goblin body out of Manticores shooting arc, where dwarves can pull Manticore darts out of goblin corpse.