Yes thank you for that example, this was another thing i wanted to bring up. At higher levels in 3.5 DnD Arcane magic is arguably the thing that makes and breaks combat. So then, how do i design mid-high level spellcasters to be a challenge but not (as you say) go on a PC murder spree.
I am under the impression that things like Finger of Death and Mordekainen's Disjunction are bad?
Save or dies are not necessarily bad. In 3.x, they can add variability and excitement to the game. Being in an aura or an area effect that does 10 damage every round and getting hit for 15 damage while you slowly bleed hp off the bad guys is somewhat predictable but it is not necessarily more fun than making a save against magic that would have slain you instantly and then watching the bad guy be consumed in fire after failing the save against your destruction spell. Save or die spells create problems when:
A. The character is essential to some part of the plot or other. If you are playing a p&p Baldur's Gate II and the Bhaalspawn character dies, then the game is over. If you are not trying to make a character (or each character's) backstory essential to the plot, this should not be an issue.
B. The character is not easily replaceable. If you are in the middle of the temple of elemental evil and everyone around you is an enemy then replacing the dead PC will be difficult. OTOH, if the character dies in the last fight in the Moathouse, the player can just bring in a new character when the party gets back to Hommlet. Maybe he sees the PCs fighting and his mysterious masked stranger jumps in and helps them. (Of course, he has to introduce himself afterward and find out that they are pursuing a similar goal). Perhaps the hero-worshipping kid brother of one of the PCs starts tagging along after him right after they get into town. ("Get lost kid." "No, way, this is fun.")
C. The character can't be brought back from the dead. If you are level 13+ and have the components for a resurection spell, then having a character die is not necessarily a big deal. Just bring him back. Some DMs don't like characters returning from the dead but in the core rules, easy resurrection shows up shortly after the save or dies start flying.
So, you will want to use save or die spells sparingly, but don't toss them out of your arsenel just because the 4th edition designers thought that they were bad. (4th edition designers had a lot of ideas about balance and game design and they tossed most of them aside five minutes after the first book was finished).
Mordenkeinen's disjunction is a different story. It is bad, not because it is a save or die but rather because it is a pain to roll out, always works on active spells, and messes with the economy of the game.
1. Pain. How many magic items do you have? Make a save for each of them. Fifteen minutes later, you're still rolling. Hey, here's my luckblade. I'd forgot I had that. I'll use it to reroll the save for my main sword. Yet another roll.
2. Always works on active spells. So the dragon is all spelled up and ready to go--Mordenkeinen's disjunction and all his spells go down, automatically. Automatically reducing the targets to a completely unbuffed state is too good.
3. Messes with the economy. In 3rd edition, your character's items are a large component of your abilities. (It's true in 4th edition too--try making a level 30 fighter without magic armor and see how long you last). Now, if you suppose that you have a fairly good save and thus lose 1/4 to 1/3 of your items on each casting of mordenkeinen's disjunction, you will have to get a lot of treasure each time it is cast just to stay where you were. No-one wants their +5 ancestral sword of awesomeness to go away, but it's even worse if you hit level 18 and your equipment is not as good as it was at level 17.
Now, it can show up every now and then without ruining the game. Kyuss used it in the final encounter of the Age of Worms campaign that I played in and it didn't ruin the game. But the spell should not be in normal use.
So, those things aside, how do you use arcane spellcasters in mid to high level 3.x. Here are some design principles I have found effective.
A. Very rarely have a spellcaster alone. Put the spellcaster in the room with a summoned devil and a nightmare and a horde of peons. Rather than having the BBEG be a wizard 3 levels higher than the PCs as an EL=Party level +3 challenging encounter, have the BBEG be one level higher than the PC but give him a summoned devil with a CR two levels lower than the PCs, a high priest two levels lower than the PCs, and a half-dozen elite guards four levels lower than the PCs (who make up for that level deficit with careful construction and support from the devil, priest, and BBEG).
B. Always have an escape plan. Your wizard will be grappled. He may be silenced. Always max his concentration ranks. You don't need freedom of movement (always) but have a minion with benign transposition to get him out. Give him dimension door. Give him a rod of silent spell. Etc.
C. Buff your allies. Those six orc elite guard fighter/barbarians four levels lower than the PCs will pack a good punch when the BBEG casts haste on them. (Especially if his cleric cast recitation and the devil included them in an unholy aura).
D. Battlefield control is your friends. Use wall of force to separate the party. Better yet, ready a wall of force to separate the party for use when the cleric is about to cast a spell. That way, his spell probably won't hit (if an attack) or benefit (if a buff) its intended target AND the party ends up split. Use wall of ice and wall of fire similarly. Bigby's grasping hand and evard's black tentacles are similarly ridiculously effective. Acid fog does a little bit of damage but it will stick PCs in the time out box for long enough for you to get the upper hand on their allies.
E. Good old fashioned area damage is still effective against PCs. Empower that fireball. Double points if it also heals your allies at the same time. Empowered fireball on the PCs and the iron golem they are fighting for the win. (Lightning bolt if you have a flesh golem ally and mass inflict serious wounds if you have undead allies).
F. Debuff. Dispel the party's wards and buffs. The fighter who was confidently fighting in your allied Mezzoloth's cloudkills won't be so cocky when his heroe's feast takes a hike. Nerf the party. Ray of enfeeblement (also comes in highly effective quickened and empowered varieties). Let's see if you can even stand up in your platemail with a -12 strength penalty. Enervation also stacks up quite nicely.
G. Save or screw. Who needs save or die? Glitterdust and the PCs are blind. The barbarian isn't so scary with a 50% miss chance, is he. (Uncanny dodge means your rogues won't sneak attack him to death but you can't have everything). Greater Command to halt and gloat as the paladin spends ten rounds watching his friends die. (Admittedly, this may be painful for the paladin's player, but that's what allies are for--a dispel magic, dispel evil, or even just a save buff should help him unless he is horribly unlucky, and if he is horribly unlucky, then he just would have spent ten rounds whiffing anyway).
H. And don't forget the finger of death. To make it more effective, rather than simply casting it, use it as a readied action to disrupt a spell. Made the save? OK, well you still take damage. DC 10+3d6+caster level+spell level concentration check or lose the spell.
