From earlier editions, Vecna Lives! was fun and should convert to 3.5Ed without too much trouble. Ditto Queen of the Demonweb Pits.
Return to the Temple of Elemental Evil was good, but only a portion of it was high-level.
You could grab any of the 3.5e Paizo adventure paths and just figure out a way to insert the PCs into the plot somewhere near the end. It might require a fairly big infodump, but if you're starting your campaign at the higher level, you can just call the earlier parts "backstory".
Practice your evil grin. Roll dice randomly behind the screen. Make notes at random times. If the dice rolls say a PC dies, they die. Have quest-givers lie, cheat, steal, or be misinformed - But only sometimes. Have most play straight, but not necessarily have the whole story, and/or have complications. Practice your evil grin. It is *Never* "just rats". Even if it is "just rats". At least once, have a loved one either be replaced by, or be, an evil shapeshifter. Make the quest reward something that gets them in more trouble - Either something illegal, that someone powerful wants, that is something powerful but generally useless itself, or simply hard to carry. Make it literal poison at least once. Practice your evil grin. If the dice rolls say a PC dies, they die. Sometimes, it is just rats, except sometimes the "rats" are in an NPCs brain. Breather episodes are fine. Even two in a row. Maybe even three. Occasionally, make something that looks like a breather episode. Then introduce the shapeshifter, disguised werewolves, secret vampire, and/or hidden demonic cult. A stay at an inn can be a great place to have a thief steal their belongings, and it introduces a plot hook. Make sure to make all the rolls and notes behind your screen, just like all the other times you did it when it was meaningless. Helms of Opposite Alignment, Werewolfism, and Vampirism, in certain ways, can all be the same plot point.Oh dear lord, I just know that if I ran a Vecna adventure, my players would be clamouring for the head.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.