Dota 2/Riki the Stealth Assassin

""I've been here the whole time.""

Riki is a melee agility carry hero who is known for being very elusive. He can stay invisible forever with his Permanent Invisibility, stalking his enemies without them even knowing. His Smoke Screen helps him evade attacks as well as disabling enemies, while his Blink Strike is excellent for chasing or escaping. All of these skills help set up his deadly Backstab, which amplifies his damage as long as he is behind his enemy.

Smoke Screen
Smoke Screen makes a lingering puff of smoke appear in the target area, silencing, slowing as well as causing enemy attacks in the smoke screen to miss. A helpful disable to let you escape enemies or catch up to them. Remember that since enemies can only be affected by the Smoke Screen if they stand in it, you should put them in the direction of where they will be instead of where they are, for a better chance of catching them longer.
 * Ability: Target Point
 * Radius: 250 / 275 / 300 / 325
 * Miss Rate: 40% / 50% / 60% / 70%
 * Slow: 25%
 * Mana Cost: 75 / 80 / 85 / 90
 * Cooldown: 13

Blink Strike
Blink Strike makes you blink behind the target unit, striking it for bonus damage if it's an enemy. It increases your mobility, but only if there are units that you can blink to. You can use it to catch up to an enemy, placing you conveniently in the position to activate your backstab, or to escape by blinking to a nearby ally.
 * Ability: Target Unit
 * Damage Type: Magical
 * Damage: 30 / 60 / 90 / 120
 * Range: 700
 * Mana Cost: 50
 * Cooldown: 20 / 15 / 10 / 5

Backstab
Backstab will let you do a bonus amount of damage depending on your agility stat provided that you attack your opponent from behind. With your invisibility and Blink Strike, it should be quite easy to get behind an opponent for a backstab. If your target is fleeing, it actually makes them more suscaptible to backstabs since their backs will be facing you.
 * Ability: Passive
 * Damage Type: Physical
 * Agi Damage Mult: 0.5 / 0.75 / 1 / 1.25

Permanent Invisibility
Permanent Invisibility, as the name suggests, lets you stay invisible permanently, only dropping it temporarily when attacking or using an ability. This is why Riki is so deadly. You can easily appear from nowhere and take an enemy by surprise. Be careful that you don't get silenced, since you will lose your invisibility for the entire duration of the silence.
 * Ability: Passive
 * Fade Delay: 3 / 2.25 / 1.5

Suggested Skill Build
Skilling Riki is rather simple, but slight adjustments must be made to fit your general situation. One thing that's consistent in all skill builds is to get your ultimate, Permanent Invisibility, as soon as you can, at level 6, 11 and 16. It is your signature ability, and you'll have much more difficulty ganking or surviving without it.

Standard skill build
Get Smoke Screen at level 1, since it is a very useful disable that lasts a relatively long time, helping you escape early ganks. Then get Blink Strike for a spammable escape mechanism and chasing tool. From level 3 you can choose whether to max Blink Strike or Backstab first. Prioritize Blink Strike if you find yourself getting ganked or going for ganks a lot, so that it becomes more spammable and gives you some extra damage. If your opponents are playing more passively or you have a great lane support that lets you farm comfortably, get Backstab to get easier last-hits. Max Smoke Screen last as its duration and slow remains constant through all levels.

Starting items
Get any combination of Iron Branches, Healing Salves and Tangos. Also get some Slippers of Agility to increase your damage for easier last-hitting.

Early-game items
You can choose to get a Magic Stick and upgrade it into a Magic Wand for some burst healing in case of enemy ganks. Get Boots of Speed for more speed and your eventual boot upgrade. You can choose to get a Poor Man's Shield if you're taking a lot of harassment. You might want to upgrade your Slippers of Agility into some Wraith Bands for some more damage and good stat bonuses.

Mid-game/Core items
For your boot upgrade, get Power Treads for extra damage, survivability and flexibility. Diffusal Blade is a great item for Riki, as it gives you a nice damage boost. The Purge ability it grants you is especially useful, as it grants you an additional disable, while it can also remove any debuffs that reveals your invisibility.

Luxury/Situational items
A Vladmir's Offering is a commonly bought item for Riki, but there are better choices. It's cheap and gives you lifesteal and damage, but it isn't worth an inventory slot during the late-game. A Butterfly is an excellent item for any agility carry, as it will give you a huge boost to your dps. You can also consider getting a Sange and Yasha for a mix of survivability and damage. An Assault Cuirass will also boost your damage with the attack speed bonus and armor reduction, but it can reveal your location to smart enemies. Lastly, a Black King Bar makes you immune to any disables, including invisibility-revealing silences, letting you take down your foes without fear of dying.

Laning/Early-game
It is a good idea to lane with a support, since it'll give you a target to Blink Strike to safety whenever you're in danger. The best lane you can be in is the safe lane, but you might want to leave it if your team has a better carry. Try to get as many last-hits as possible and reach level 6 quickly, because you're very vulnerable to harassment and ganks before you have Permanent Invisibility. Try to position yourself to proc Backstab when going for last-hits, but don't attempt it if it means putting you in range of an enemy hero's attacks or disables.

After getting your ultimate, have a habit of checking the enemy supports for anything that can reveal invisibility, such as Sentry Wards and Dusts of Appearance. These items will strip you of your primary form of protection, which you will need if the other team attempts to gank. An odd number of Sentry Wards means that one is placed nearby, so you must be more careful not to reveal yourself.

You can also participate in ganks as you have the tools to do so, having invisibility, a great disable with Smoke Screen and a chasing tool/escape mechanism with Blink Strike. Be sure to check your targets for invisibility-revealing items so that you won't be detected early or the gank may backfire.

Mid-game/Teamfights
You start to become a real threat by this stage of the game, as long as you weren't held back and countered too much. Your Blink Strike should be quite spammable and your Backstab damage should be high enough to take down weaker heroes quickly. You're still relatively fragile for a carry, but your invisibility and the purge ability of a Diffusal Blade will make you more elusive. You must still watch out for things that can take away your invisibility. Some enemy heroes might start carrying a Gem of True Sight, which will make you much less effective as long as you're in its presence, so make them a priority target.

When a teamfight starts, you usually don't want to jump straight into the fray, since you'll be eliminated quickly by the initial wave of spells and attacks. Wait until your enemies are softened by your allies before attempting to kill them. Your Smoke Screen is very useful during these teamfights for disabling spellcasters and slowing carries. In fact, you can initiate a teamfight by casting Smoke Screen over an important enemy hero like the carry or the initiator and eliminating it. You are also great at taking out wounded enemy heroes after a successful teamfight, as a Smoke Screen combined with a Blink Strike and the bonus damage from Backstab will make it very difficult for your foes to fight back.

Late-game
By this stage your damage output will be higher than ever, but you'll still get outmatched by certain hard carries. Your strategy is relatively simple now, just Blink Strike to your target, cast Smoke Screen if you need to slow them or give yourself some extra protection, then wear them down with physical attacks. Always aim to attack their back for the bonus damage from Backstab.

Skill synergies
All of Riki's abilities help him land a Backstab. His Permanent Invisibility lets him position himself behind his targets. His Blink Strike automatically places him behind his opponent, while his Smoke Screen will usually force foes to move out of it, exposing their backs to him.

Hero synergies
Riki synergizes well with any support hero with good disables, such as Crystal Maiden, Venomancer and Vengeful Spirit. They not only help harass the enemy, giving him an easier time last-hitting, they can also hold your foes still for you to get early kills.

Countering Riki
Anything that reveals invisibility will counter Riki, as he has relatively low health for a carry and doesn't have any way to survive without his invisibility and an allied target to Blink Strike to. Sentry Wards, Dusts of Appearance and Gems of True Sight are all obtainable from the shop for a relatively low price. Slardar and Bounty Hunter are also good counters of Riki, as their ultimates will reveal him for its entire duration. Heroes with silences can also prevent him from staying invisible.