I am a level 22 Ice wizard. I was doing a quest in Krokotopia that required me to fight a Life boss. I figured that since it was Life and kept casting Death shields, it was resistant to Life and vulnerable to Death. After defeating his smaller helper, I went on to him. I cast an Evil Snowman, when, much to my surprise, he resisted almost half of the Ice attack! Since all the attack spells in my deck were Ice, I was not able to finish him off, and I was defeated.
Here's another scenario: you are fighting an average run-of-the-mill enemy, when you get him down to about 60 health points. You are a Death wizard, and the enemy is also Death. You want to cast a 65 damage zero pip wand spell. However, you don't know what percentage that enemy is resistant to Death. You cast the spell anyways, but it only does 58 damage. You do not defeat the enemy.
I think that it would be a great idea to include a tab in your spellbook that would be an "Enemy Handbook". It would possibly show what enemies you have battled, what their weaknesses and resistances are (and what percentage), how much health they have, what level they are, and so on. I cannot tell you how many times I have not killed an enemy because my spell was one or two damage points short. With a little math, you could find out the exact damage you will do (or the exact range of damage), and cast the appropriate spell. Not only would this help you in battle, but this could also help you in prepping your spell deck, so that you may include the appropriate spells. For example, if I am battling an Ice enemy, I usually include my Ice Prism to convert Ice to Fire. However, I'm not sure if that enemy is resistant or vulnerable to Ice, so I'm not completely sure if I should use it or not.
I think it would be awesome for KingsIsle to include a feature such as this in an update.
