Most Insane Artifact?

[Dyslexic Q-Thief]

In my current game, I made a Grand Staff of Power with:

* +20 Spell Skill
* +3 to hit
* -4 Spell Save
* 4x Phantom Beast

It costs over 5,000 Crystals, but I gave to an Illusionist and now he can annihilate Elite units in a single shot. With a ring of Flying, Magic Immunity, and Invisibility, he can take out entire armies by himself without a single scratch. To add insult to injury, there's four Phantom Beasts in it, just as if it wasn't absurd enough.

What's your most expensive artifact ever?

[Iluvalar]

I found the "theodores liberator" in a recent game
+6 att
+20 skill
-4 spell save
creature bindingx4

There are many pretty item in the game, but this one is one of my favorites.

[Implode]

I found or made 3x -4 spell save items and gave to a hero just to prove that it allowed him to cast 'drain power' with a huge enough resistance penalty that he could make undead great drakes. Not that it was overly useful, just did it for a bit of fun :)

[Iluvalar]

Drain power ? it's an overland spell doesn't it ?
Maybe you meant life drain ?

Are you sure -spell saves are stackable ? Mabe i'm wrong but i'm pretty sure I already tried it and it didn't seemed to work...

[nyarlathotep]

Miscellaneous magic item with Flight, Invisiblity, Guardian Wind, and Magic Immunity.