Grimrock

I'm reading through the asset definitions and I'm not seeing anything in the items definitions that behaves like existing tomes.
I wanted to make a tome like the Tome of Fire, but without being able to negate the fire bonus, and figure out how to increase ice magic by three, that's kinda hard.

Hint: you need to implement the onUseItem hook in tome item's definition. The same hook can be used to create potion effects btw.