I've seen games where status ailment spells still do damage on the enemies they're cast on, even if they are immune to the effect themselves. If Sleep fails, the enemy still gets about 20 damage (insert number for your game), same for if Death fails. The enemy still gets a good chunk of damage, which might still kill them, anyway! Of course, the same is true of your party.
I like the ideas I've seen before that higher level spells have certain effects that dramatically improve earlier-tier spells. Ice 3 might freeze, Ice 2 chill, and because all those effects are stacked, Ice 1 which would otherwise be useless just might end up shattering the enemy (or party member...) equaling instant death. But too much use of Ice 4 or Fire 4 might just change the climate of the area instead, and the party just might bring about the next Ice Age or Runaway Greenhouse Effect.
I like the ideas I've seen before that higher level spells have certain effects that dramatically improve earlier-tier spells. Ice 3 might freeze, Ice 2 chill, and because all those effects are stacked, Ice 1 which would otherwise be useless just might end up shattering the enemy (or party member...) equaling instant death. But too much use of Ice 4 or Fire 4 might just change the climate of the area instead, and the party just might bring about the next Ice Age or Runaway Greenhouse Effect.
