The Basics of Slark:

Slark is a powerful ganker, initiator, and semi-carry. He is focused mainly on burst damage and taking the enemy by suprise. Make sure to know if the enemy has good vision of the map. Slark , played right, will snowball out of control and dominate the game with enough farm. Overall, to play Slark you need to know four things:
1. How to Gank
2. How to last hit effectively
3. How to aim (with Pounce)
4. How to time your attacks / abilities

If you are unfarmiliar with Slark, I would recommend the following video by DotaCinema:

Items:

Purchase order:
Starting items > Orb of Venom > Magic Wand > Boots of Speed > Power Treads > Skull Basher > Shadow Blade > Orchid Malevolence / Desolator > Daedalus

Starting Items:
Stout shield > 3 Iron Branches > Tangoes > Clarity maybe?

Luxury:
Mask of Madness / Vladimir's Offering / Abyssal Blade / Eye of Skadi / Mjollnir / Butterfly / Rod of Atos.


Abilities:

1. Pounce
2. Dark Pact
3. Pounce
4. Essence Shift
5. Pounce
6. Shadow Dance
7. Pounce
8. Dark Pact
9. Dark Pact
10. Dark Pact
11. Shadow Dance
12. Essence Shift
13. Essence Shift
14. Essence Shift
15. Stats
16. Shadow Dance
17+. Stats

Dark Pact:
"After a short delay, Slark sacrifices some of his life blood, purging negative buffs and dealing damage to enemy units around him and to himself. Slark only takes 50% of the damage."

Delay: 1.5
Damage: 60 / 120 / 180 / 240*

* Damage comes in 10 pulses timed 0.1 seconds apart. These pulses remove most debuffs. Especially helpful for removing Bounty Hunter's Track. Can be used to remove stuns from projectiles like Wraith King's Wraithfire Blast.

Pounce:
"Slark leaps forward, grabbing the first hero he connects with. That unit takes damage and is leashed to Slark, and can only move a limited distance away from Slark's landing position."

Range: 700
Leash duritation: 3.5 seconds
Leash Radius: 325
Damage: 60 / 120 / 180 / 240

Note that it whoever you Pounce over first. NOT who is closest to your landing spot. Also note that it only leashes actula heroes, not illusions or creeps, so this is good against heroes that rely on illusions, such as Phantom Lancer, Naga Siren, Terrorblade, Chaos Knight, etc.

Essence shift:
"Slark steals the life essence of enemy heroes with his attacks, draining each of their attributes and converting them to bonus Agility."

Effect duritation: 15 / 30 / 60 / 120
Enemy Str. Agi. Int. : 1
Agility gained on each attack: 3

This effect does stack and that means after you are gaining 3 damage per attack. So, after 10 hits, you'll have 30 extra damage! Soon you will find that after teamfights you might have up to 15 stacks, which equals 45 extra damage. With a high level of essence shift and a skull basher, you are capable of taking on Roshan by yourself!

Shadow Dance:
"Slark hides himself in a cloud of shadows, becoming invisible, gaining bonus movement speed and regeneration while not seen by enemies. Attacking, casting spells, using items, and true sight will not reveal or end Shadow Dance."
Bonus Movement Speed: 30% / 40% / 45%
Bonus Regen: 3% / 5% / 7%

This skill is what makes Slark so unkillable. You thought a Heart was annoying? Take this Ultimate! It gives you (at max) 7% of your current HP as Regen when not in enemy vision. So if your current HP is 1400 and your shadow dance is maxed thats 200 extra regen! Making sure to check if the enemy has wards and where they put them is what will make or break a good Slark. But dont spend all your time looking for wards either. Instead, have your support use a Dust on common ward areas.

Slark is a great ganker throughout the game, especially with a Shadow Blade. His Pounce makes him even more-so.

When you gank with Slark you are going to want to activate Dark Pact (Since it has an activation time) then Pounce on an enemy from a cliff, behind some trees, or any other hiding spot. So you with leash them so they don't escape, Dark Pact will melt through their health, and then you can auto-attack at will. Your Essence Shift will increase you damage the more you auto-attack. The same applies to chasing enemies.

Well who should I hunt when?

Early - Mid game ( 0 min - 10 min ) - Your main targets are going to be squishy supports like Crystal Maiden, Rubick, etc. They are a great source of gold and exp. and when you kill them they lose gold and exp, plus thay have to take a trip back to their lane or buy a TP scroll ( P.S.: TP scrolls are CHEAP. If you are new it seems like alot, but it's not). In that valuble time your new job is to harass the carry and get as many lats hits a possible when the support is gone.

Mid game ( 10 - 20 min ) - This is the time to track down and kill carries and tanks before they are difficult to kill in the late game. Often in this time you can take a 1v1 but NEVER under ANY circumstance are you to go in alone against more than 1 hero, UNLESS, one of them is a squishy support. And even then you MUST be on full or near-full health (which is easy with Slark). Shadow Blades are good for this purpose and gives you a chance to escape / heal if things get rough.

Late game ( 20+ min ) - Do as you've done before, and kill, kill, kill. You should have good farm by now and your attacks should cut through enemies like butter. Keep killing, get Luxury Items.

Roaming is ( in a nutshell ) going around the map caually, and killing people doing it. Picking off a Crystal Maiden here, a Sven there, getting as much gold as possible.
To do this you are going to want a ganking buddy with a serious stun. Some heroes with good stuns are: Vengeful Spirit, Puck, and Dragon Knight. When stunned you jump in there with Pounce for a quick kill and run as fast as you can.

Shadow Dance is a unique ultimate with a passive and active aspect. The passive gives you regen and movement speed when you are outside of enemy vision (creeps included, and on mini-map). the active turns you invisble ( But not completely, you have a big black clound floating around where you are ), giving you the chance to regen and escape with your movement speed. It lasts for 4 seconds (which is actually alot). Also this ability puts a small symbol over your HP bar. this symbol can be used as a sort of 'radar' to know if a invisible hero is following you.

How?

When you are seen by the enemy the icon disappears and you loose the regen and movespeed. So if the icon disappears and you start to move slower when nobody is around, most likely a Riki or other invisible hero is following you. Use this to the fullest.

Shadow Blade on the other hand, gives you REAL invisibility (No smoke cloud). This can be used to evade chasing enemies, get some quick regen, sneak up for a Pounce, and moving around quicker.
SeaOtter's Guide to Tricking your Enemies with a Shadow Blade:

Step 1: Run from enemy
Step 2: Run into spaces between trees
Step 3: Let them come and chase after you
Step 4: Activate Shadow Blade
Step 5: Run back the way you came
Step 6: Laugh in the shadows as your enemy scrambles around looking for you.
Step 7: Also works if you run in Fog of War*

*You can tell if you are because of ultimate. See first two paragraphs

With practice you will be. You will miss Pounces (I don't), you will forget to check for wards (I don't), and, if you are new at MOBA's, will probaly feed a couple of games before you get good at Slark. But all this practice will pay off in time. Someday, maybe even you will surpass me. I look forward to that day.

These are all the secrets of Slark I know, and I am passing them on to you. Use this knowledge wisely.

Farewell random reader. This is my first guide and you will have probably found flaws in it by now. Please tell me about them. Thank you for reading this guide. Please rate and subscribe.

-SeaOtter

P.S. If you are intrested, add me to join my new team... ArchAegis.