Well, first I'd like to say that this is my first suggestion and concept of a LoL hero, so would be nice from you guys to support me with honest and sincere feedback. I'm totally open to suggestions.

Appearance: Brazel is a grown-up man dressed in leather clothes, as well as the traditional long coat. No mistake that he'd look like a traveler if wasn't the two long swords he carries in the back. He do always look calm, and his long, mistreated hair always partially covering his face, hiding some of his feelings.

Overview:
Health Average
Spells High
Attack High
Difficulty Very High

Before going deeper on him, a warning: he has a very complex playing style. Based on his ultimate, he is basically a 2-on-1 champion, which means you must learn how to play with two heroes at once to handle hum efficiently. That's why I'll start explaining his ultimate.

(R)Personality Flip: Brazel wipes out for a second, recovering from the personality change. After that, he assumes the other personality, applying the effects.
Passive: for each rank, he permanently gains 20 Attack Damage and 50 Ability Power.
Cooldown: nothing, but can't happen again in 1 minute.

(Passive)Killing Maniac: According to the current personality, Brazel doubles every damage he deals to certain enemy champions. It will be doubled again if he critically hits, but critical damage increase will only affects basic attacks damage. However, the damage is diminished by 20% if not doubled.
Ranged: double damage champions with more AP than AD.
Melee: double damage champions with more AD than AP.

Knowing that his playing style core is the personality changes, I'll explain now each personality.

1st Personality: Ranged
Brazel starts the game assuming this personality. He is a calm, cool-minded AP ranged carry. His basic attacks are masses of unstable, pure energy that hurts enemies on impact. Those energy masses explodes on contact if critically hits.
Role: Mage

(Q)Redirect: fires a blast of energy in a line, dealing magic damage to the first enemy it hits and knocking it 50 units the opposite direction it's facing.
Damage(per spell rank): 70/110/140/180/230 + (0.4*AP) + (0.1*AD)
Cooldown: 9 seconds
(W)Destabilizing Wave: Brazel channels for 0.5 seconds then fires a wave of strange energy in a cone. Champions hit are silenced for (0.75*spell rank) seconds.
Cooldown: 13 seconds
(E)Brain Collapse: Brazel surges and explodes the energy flowing over his body. Enemies 50 units away from him are feared and will run away from him for (0.5+0.25*spell rank) seconds. Unis killed while feared will fear other units 50 units away from it for the same time. Range is increased for (0.03*AP+0.01*AD) units.
Cooldown: 25 seconds

2nd Personality: Melee
When Brazel assumes this personality, he unsheathes his two long swords and is body stops surging energy. Instead of acting cool-minded, he begins to act like a impatient, bloodthirst assassin. His attacks are simply sword swings, whirling in the air and striking the enemy when critically hits.
Role: Melee, Assassin, Carry

(Q)Vorpal Assault: Brazel leaps into the air and swings his swords fiercely, striking nearby enemies. Deals Physical damage 30 units away.
Damage(per spell rank): 50/80/130/150/190 + (0.4*AD)+(0.1*AP)
Cooldown: 5 seconds
(W)Iron Wire: Brazel fires an iron wire hidden in his arms, wrapping the enemy and pushing himself to the target. If the wire crosses over an enemy, physical damage is dealt. When Brazel arrives at the target's back, strikes with both swords, dealing double damage(not increased by passive).
Damage(per spell rank)(middle enemies): 15/30/40/55/70 + (0.1*AD)+(0.05*AP)
Reach: 120 units
Cooldown: 12 seconds
(E)Bloodbath: Brazel starts licking his swords' blood, satisfying his bloodthirst. Everytime he strikes an enemy, he regains some health.
Passive: +(6% per spell rank) lifesteal.
Health recover(per spell rank): 7/10/13/17/21
Cooldown: 18 seconds

Suggested items: this is my point of view about him, so feel free to suggest a different set of items.
Sorcerer's Boots or Berserker's Greaves according to the one you might wanna focus
Rabadon's Deathcap
Nashor's Tooth or Phantom Dancer according to the boots
Trinity Force
Frozen Mallet
Infinity Edge