taken from lol wiki:For nearly twenty years, Fiddlesticks has stood alone in the easternmost summoning chamber of the Institute of War. Only the burning emerald light of his unearthly gaze pierces the musty darkness of his dust-covered home. It is here that the Harbinger of Doom keeps a silent vigil. His is a cautionary tale of power run amok, taught to all summoners within the League. Decades ago, there existed a powerful rune mage from Zaun - Istvaan. At the end of the fifth Rune War, he became one of the League's first summoners. Too much a prisoner to the old ways of magic, Istvaan stepped further and further outside the rules of conduct in the League. In what was ultimately his last match, his reach finally exceeded his grasp. Sealing himself inside the easternmost summoning chamber, he began incanting the most forbidden of rituals - an extra-planar summoning.

What exactly happened inside that chamber remains unknown. No champion came to represent Zaun that day in Summoner's Rift. Only silence echoed back from repeated knocks on the chamber door. The first apprentice who entered was cut down immediately by an unearthly scythe. What few who followed and survived were driven mad by fear, mere husks of men gibbering about crows and death. Afraid of the evil even Istvaan could not control, the League sealed all exits to the chamber, hoping they could contain what they could not destroy. Years went by, but the wooden figure within never moved save to slay any foolish enough to enter. Seeing no recourse to reclaim the chamber, the Council instead devised a use for Fiddlesticks: executioner. While he comes to life and seemingly abides by the rules of summoning in the Fields of Justice, what he awaits inside his chamber is unknown. His unmoving face yields no clues, and his scythe stands ready to strike down any who stand before him.

"Those who say 'you have nothing to fear but fear itself' have not yet felt the crows."

can't take credit for alot of the extra info have taken it from other sources to build it out this is the way i jungle with fiddlesticks just wanted to share :)

taken from lol wiki:

Negative ResistanceEdit

If a target has negative magic resistance, the amount of bonus damage is equal to the amount of damage reduction caused by that positive amount of magic resist. This sounds confusing and is better illustrated with an example.

If a target has 10 magic resistance, they take 9.1% reduced damage (formula from Magic Resistance).
Therefore a target with -10 magic resistance would take 9.1% bonus damage.
So if you cast a spell that does 100 magic damage on the target, it would take 109.1 damage instead.
If a target has 20 magic resistance, they would take 16.7% reduced damage.
Therefore a target with -20 magic resistance would take 16.7% bonus damage.
So if you cast a spell that does 250 magic damage on the target, it would take 291.7 damage instead.
Note that magic penetration (percentage or flat) has no effect on targets with negative magic resistance.