Ok, i've been looking around the forums and haven't noticed any ninjas... Though i realize it would be rather difficult for me to create a backstory for some (demi)godlike ninja I shall still attempt to.
Backstory (i'll leave it open for any suggestion or alterations)
Following the events of the [enter generic village name here] slaughter, the Empire of [enter generic evil empire name here] found, that to prevent such miscommunications in the future, some measures must be taken. And thus was the Order of [enter generic secret peacekeeper order name here] created.
The Order consisted of 13 of the finest warriors of the Empire. They were all overly powerful, with beastlike strength and fast instincts. They were stripped of their names and former titles and made soldiers with benefits for the Empire. The Empire used them for the assassinations of many outstanding members of the society. Thus they hoped to hold power in their own hands.
With new and spectacular advances in medicine and science the Empire prospered. The Empire felt, that to keep power over the people and more importantly, over the order, they had to be given a thorough brainwashing. The Order went along with it - they were given shots to increase their strenght and agility, but at the same time to make them more obedient to their leaders.
As time went on the Empires leaders aged and grew more and more suspicious of eachother, each one hoping to keep holding on to the power that they have, they sought to destroy eachother. Each one calling for the Orders full help, the control over the Order slipped. The leader of the Order - called Shin by his superiors - ordered a revolt against their former masters.
He ordered his subordinates to commit suicide after the deed was done, for he was the only one to reveal the truth of their leaders and bear the burden for their heinous crimes. The community, now shocked and outraged went into panic. Shin knew, if the people were to stand, if the Empire was to stand, he had to ascend to godhood and take position as sole leader of a new Empire - the Empire of Truth.
Type: Assassin (light side)
Stats: (waiting for suggestions)
HP: 1540 (+105/lvl)
HP regen: 2.32 (+0.16/lvl)
Armor: 230 (+25/lvl)
Mana: 952 (+93/lvl)
Mana regen: 2.92 (+0.37/lvl)
Damage: 115-128 (+6.9/lvl)
Attackspeed: i have no idea of how the numbers work on this one, so i say faster than average, a bit slower than UB
Range: Melee/10(11/12) yards
Movespeed: 6.3
Skills: he would be a demigod that switches between 2 weapon styles, but instead of having 6 active abilities, he would still have have 4 (1 skill slot to change stances, 1 skill slot that changes along stances, and 2 that stay the same no matter which stance
stances: switches between stances initially take 3 seconds, no cooldown
melee (sword (katana)) - regular run of the mill melee attack
ranged (shuriken(s)) - the range of these im not quite sure of, maybe a tad less than UB's venom spit and at max range not enough to hit towers attack damage of each shuriken is cut in half and each seperate shuriken is a projectile on its own (each shurikens damage is its own, allowing each shuriken to crit seperately and dodged separately, but an attack is still one attack, meaning that an attack still has the same probabilty of inflicting a status effect)

A (chemical instability, active, 1 second cast time, 20 second cooldown) - Shin injects himself with a performance enhancing drug gaining heightened strength and durability. While under the effects of this drug Shins body becomes chemically unstable and if killed while effect is active will explode dealing set amount of damage to all nearby units and buildings.
- gains +30 damage and 2% damage reduction, if killed explodes for 250 damage, 4 yard aoe, lasts 20 seconds, 300 mana
- gains +50 damage and 4% damage reduction, if killed explodes for 450 damage, 7 yard aoe, lasts 20 seconds, 400 mana
- gains +70 damage and 6% damage reduction, if killed explodes for 700 damage, 10 yard aoe, lasts 20 seconds, 500 mana
- gains +90 damage and 8% damage reduction, if killed explodes for 900 damage, 10 yard aoe, lasts 20 seconds, 550 mana
- the drug is now incredibly potent, permanently enhancing Shins damage until killed by +1,5 each injection, 10% damage reduction, if killed explodes for 1100 damage + 20 damage each stacking injection, 10 yard aoe, lasts 20 seconds, 600 mana
B (lightning reflexes, passive) - All those years of training have given Shin lightning reflexes, enhancing his dodge.
- gains +5% dodge
- gains +7% dodge
- gains +10% dodge
C (smokebomb, active, 0,5 second cast time, 25 second cooldown) - Shin throws a smokebomb at his feet creating a thick smoke cloud. Enemies caught in the smoke cloud are disoriented. Structures are uneffected.
- enemies movement and attackspeeds are slowed 5%, 3 yard aoe, lasts 4 seconds, 450 mana
- enemies movement and attackspeeds are slowed 10%, 5 yard aoe, lasts 6 seconds, 550 mana
- enemies movement and attackspeeds are slowed 15%, 7 yard aoe, lasts 8 seconds, 650 mana
- enemies movement and attackspeeds are slowed 20%, 10 yard aoe, lasts 10 seconds, 750 mana
D (slash, active, sword stance, 0,1 second cast time, 7 second cooldown) - Shin slashes targeted enemy with his sword.
- 250 damage, 300 mana
- 450 damage, 450 mana
- 600 damage, 550 mana
- 700 damage, now aims for vital organs giving it a 25% chance to deal 1,5x damage, 650 mana
- 800 damage, now aims for vital organs giving it a 35% chance to deal 2x damage, 750 mana
E (kendo, passive, sword stance) - After practicing for many years Shins soul and sword merge, allowing Shin to execute attacks with more precision.
- 25% chance for 1,2x damage
- 35% chance for 1,5x damage
F (throwing mastery, passive, ranged stance) - Shin gains better control over his shurikens increasing their range and increasing number thrown.
- +1 yard range, now throws 2 shurikens at once
- +2 yard range, now throws 3 shurikens at once
G (stance perfection, passive) - Shin has mastered control over his weapons.
- +10% attack speed, stance change now takes 0,5 seconds
H (shuriken storm, active, ranged stance, 0,5 second cast time, 15 second cooldown) - Shin throws a flurry of shurikens in front of him in a cone, up to a range no longer than his own.
- throws 3 shurikens, each shuriken dealing 100 damage, 350 mana
- throws 5 shurikens, each shuriken dealing 110 damage, 500 mana
- throws 7 shurikens, each shuriken dealing 130 damage and bouncing once, with the bounce dealing 10% of the original damage, 650 mana
- throws 9 shurikens, each shuriken dealing 150 damage and bouncing twice, with the first bounce dealing 15% of the original damage and the second one dealing 5% of the original damage, 750 mana
- the shurikens are now poisoned anyone hit by the shurikens in any way will be dealt 30 damage per second for 7 seconds, 850 mana
Appearance:

Anyway this is pretty much what i had in mind with his appearance, maybe would be a tiny bit taller than Regulus. (picture found on Elfwood, all legal rights held by its author)
Anyway this is pretty much the basic idea... Suggestions may be added and the material given here may be improved upon. And a factoid: shin means truth in Japanese.
EDIT: added stats and stat growth, pantheon side