Dota 2/Mortred the Phantom Assassin

Phantom Assassin is a melee agility hero who is usually played as a hard carry. She is quite fragile, but has the chance to strike harder than any other hero. Her Stifling Dagger helps her last hit with ease and is a decent harassment tool. It also lets her catch up to enemies and use her Phantom Strike. Using Phantom Strike she can chase down enemies or make a swift escape with an ally. Her Blur, even though it doesn't fully make her invisible, can be effective at evading enemy attacks. Her ultimate, Coup de Grace, is the best critical strike ability in the game. When it activates, she can do tons of damage with her physical attacks, enough to kill weaker heroes in one hit.

Stifling Dagger
Stifling Dagger throws a dagger at the target, slowing it and dealing pure damage. The damage is halved on enemy heroes. It's damage is rather pathetic, so against heroes you will only use it for its slow. It can be used to last hit creeps from a distance during the laning phase. The short cooldown and low mana cost ensures that you can spam it repeatedly if needed.
 * Ability: Target Unit
 * Affects: Enemy Heroes
 * Damage Type: Pure
 * Damage: 50 / 100 / 150 / 200
 * Slow: 50%
 * Duration: 1 / 2 / 3 / 4
 * Mana Cost: 30 / 25 / 20 / 15
 * Cooldown: 8

Phantom Strike
Phantom Strike makes you blink to an enemy or allied unit, gaining bonus attack speed if it's an enemy. It is great for initiating kills and chasing down heroes, as you are almost guaranteed to do a lot of damage upon blinking to the enemy. Its great range means that you can strike enemies even if they're quite far away. You can also use it as an escape mechanism, by teleporting to a friendly unit when in danger. With a short cooldown and low mana cost, you never have to worry about not being able to use it during skirmishes.
 * Ability: Target Unit
 * Bonus Attack Speed: 100%
 * Max Attacks: 4
 * Range: 1000
 * Mana Cost: 50
 * Cooldown: 14 / 11 / 8 / 5

Blur
Blur makes you translucent whenever enemy heroes are nearby, making you harder to see and invisible on the enemy minimap. It also gives you a chance to evade enemy attacks. Even though you are still visible, it can be hard for enemies to keep track of you during chaotic teamfights. Since players usually check their minimaps as well as the main map for enemy heroes, they can also potentially miss your presence. The evasion also makes up for your fragility, letting you get the upper hand in duels with other heroes.
 * Ability: Passive
 * Evasion: 20% / 25% / 30% / 40%
 * Radius: 1600

Coup de Grace
Coup de Grace gives you a chance to do a ton of damage in a critical hit. It is certainly the strongest critical strike type ability in the game, letting you do more than 4 times your normal damage at level 3. With some damage-increasing items, you can potentially kill weaker support heroes in one lucky hit. Once your attack speed becomes high enough, you can get multiple crits while attacking enemies, draining away large chunks of health on even the most farmed carries.
 * Ability: Passive
 * Critical Damage: 250% / 350% / 450%
 * Critical Chance: 15%