Murky is a very strange hero to play as. He can easily kill anyone, but can also be killed really fast. Since his Trait allows him to revive in 5 secs, his death doesn't cause a team disadvantage.
In low ranked games people underestimate the damage from the pufferfish or the importance of finding the egg. But on the higher competition, the enemy will always be on top of you.

Murky MIGHT be a female, because he/she lays eggs, but it not certain.

Murky can come up with the most beautiful strats, thanks to is pack of abilities which give him power to do everything: ganks, laning, split-push, objective steals.

Slime is a very powerful ability. Its slow increases the damage potetial of the Slime+ Pufferfish combo. It's low cooldown allows Murky to pursue targets, as the slow continues for 8 secs. Also, it does more damage to heroes that were already slimed, this means you have to spam it everytime. Since Murky doesn't have Mana, you can be always using it, revealing cloaked enemies.

Pufferfish is the source of most of your damage, if you follow the build above, you'll be doing tons of damage in seconds. Like I said above, in low ranked games, your pufferfish will be ignored, therefore use it aggressively. If the enemy avoid standing in range of the Pufferfish, then you can us it as a zoning tool.

This ability is what makes Murky the most annoying hero in HotS. Any good Murky (anyone with a ping under 100ms), will use Safety Bubble at low health, just to annoy whoever is pursuing him. Until you get Bubble Machine be careful how you use this though, only engage if you have the Safety Bubble off cooldown.

Safety Bubble is already annoying enough, but Murky's passive makes all zeratuls mad. As you can ready from the icon, you'll be able to spawn an egg from the which you'll respawn after 5 secs EVERYTIME UNTIL THE EGG IS DESTROYED. Unlike Diablo's souls, this egg will always make you appear in 5 secs. And you can choose where you want to spawn. Always change your egg placement, put it near objectives when they are up, but when they end, hide it somewhere. Zeratul's favourite game is to walk around and do everything to get your egg, so be sure to not give any clues about where it is at. Hidden Assault helps a lot against egg hunters.

This heroic gives Murky a lot of defensive and aggresive power, as you can spawn this near an objective to scare enemy heroes. To use this heroic you have to remember that it can go through terrain and it only attacks structures and heroes. Structures take half the damage, so it's not a very good ability for pushing. It's also very small meaning anyone can escape easily. You can upgrade (lvl.20) the duration and the lenght but not the width so it's not worth to upgrade it at all.

If you feel you got the guts to gank like a boss take Octo-Grab. This allows you to stun an enemy hero for 3 seconds. That's a lot of time to kill if you have Kael'thas or any burst damage dealer. The lvl.20 talent allows you to do 900 damage (300damage*3hits). If you land the combo correctly ( Pufferfish+ Slime+ Octo-Grab) you can deal loads of damage in seconds, even if you are alone.

Damage Build:

This build is based on doing as much damage as possible with Pufferfish. It has an easy to land combo ( Slime> Pufferfish> Rewind). It can be used for clearing lanes, getting mercs and sometimes for zoning and ganking. It sometimes can be hard to land Pufferfish correctly during a pursue, so I made the Gank build. You can use either heroic abilities.

Gank Build:

If you are with a Zeratul and/or Nova, you can pick easy targets with them. But sometimes they don't accept death right away, that's why we increase the slow and decrese cooldown of Slime, also, you can go in and out with Bolt of the Storm and Safety Bubble. To secure the kill, you use Envenom, Blood for Blood and Octo-Grab, which will surely kill the enemy. Easy combo too Slime> Pufferfish> Envenom> Blood for Blood> Octo-Grab. If you dont take ... And a Shark Too!, take rewind for double Pufferfish.

Defensive Build:

If the enemy team is too aggresive, you will need to use Safety Bubble more often to escape from them. If you see that one of them is by himself, it is either a bait or an unawared enemy, pick him with Octo-Grab. Otherwise, take March of the Murlocs to scare them.

Tier 1

Block- This talent is completly useless, since it only protects against Basic Attacks and not abilities. A Nova can easily 1-shot you.

Bubble Breeze- This talent helps you escape from teamfights and failed engages. It also can be used to easily pursue an enemy

Assault Egg- The extra sight is good, so you can know if anyone is close to your egg. But the health increase is useless, since your egg is going to be destroyed anyway.

Bribe- I don't take Bribe very often because in late game you can get mercs really fast thanks to Pufferfish+ Slime.

Tier 2

Bigger Slime- This talent is kind of useful if used with Slimy Pufferfish, but it doesn't have as much impact as the other talents in this tier.

Tufferfish- In low ranked games, people underestimate the damage from pufferfish, so they don't attack it. In high ranks, they will use burst damge to melt you and your pufferfish, so it will never blow. This means that this talent is COMPLETLY USELESS

Livving The Dream- Just by reading the name you know it will be a good talent. After being alive for 75 secs, you will get a 20% Ability Damage increase. This means at lvl.20 you'll be doing 1000 damage with Pufferfish in non-slimed targets.

Envenom- Murky is very squishy, so if you're not careful, you might end up getting caught when trying to use Envenom. However, if you know what you're doing, I encourage you to use it, because it can secure a kill (if they don't have a support).

Tier 3

Slime Advantage- Dealing 100% more damge for 8 secs can be useful if the enemy team is mostly melee, if not, choose other talent.

Hindering Slime- Although this talent is useful for pursue, many other heroes have a way to reach the enemy (assuming you're not alone) like , ,etc...

Compressed Air- The most obvious choice. With this you can damage an entire minion wave. Together with Wrath of Cod it can insta-kill minions.

Clairvoyance- Even though this can detect enemies, they would probably attack you before you even use clairvoyance.

Heroic Ability

March of the Murlocs- This heroic can be used in many ways:

Defend/Attack an objective like a tribute, a dragon knight shrine or a temple;
Attack the enemy structures, and stop them from defending since the murlocs do lots of damage;
Defend Your structures
Secure/Steal a boss

The damage from the heroic is incredible, EACH murloc deals 210 at lvl.20, plus the 15% slow. It makes easy kills, but it is confined to a small space, so its easy to escape from.

Octo-Grab- If you're not alone, this heroic is awesome. It allows you to easily gank and pick weak targets with the help of or . If you're alone, be sure to attack from the enemy side, so you can bodyblocks more.

Tier 5

Continuous Slime- Although less cooldown means more damage, slime has a melee range, so you have to put yourself at risk do a little bit more damage. It's simply not worth it compared to the other talents.

Wrath of Cod- This is the talent that boosts the Pufferfish+ Slime combo. With Living the Dream+ Compressed Air+ Wrath of Cod you'll be clearing lanes and mercs like it was nothing.

Bubble Machine- Take this if the enemy team is very aggresive. This talent allows you to go in and out of fights and to protect yourself and others from Nova's snipe.

Hidden Assault- With the stealth you can put your egg in the enemy's base and everytime you respawn get out of it. This also ensures that a Zeratul doesn't scout your egg so easily. Aslo very useful against Zagara's creep.

Tier 6

Slimy End- The only heroes with an excuse to jump into the middle of a fight when almost dying are Tyrael and The Butcher. Even if you were trying so help a friend escape, why the [censured] would you use slime on death?

Slimy Pufferfish- Very useful with Wrath of Cod, as it allows you to slime from a distance, slowing your target. This makes pursues easier and clearing lanes as easy as clicking 1 button (with smart-cast on).

Rejuvenating Bubble- Very useful with Bubble Machine and Bubble Breeze. You can troll your foes by using E and healing all your health back up, right before their eyes. Very good against agressive teams.

Blood for Blood- It can deal a good amount of damage if used with Envenom. The healing isn't very useful though since your Max Health on lvl.20 is 1390 and you can heal really fast.

Tier 7

Never-Ending Murlocs- Never-Ending is not the right expression for extra range and 2 secs extra of slow. It's harder to avoid the heroic, but not impossible. Might be useful is some cases.

... And A Shark Too!- This makes me laugh everytime... It makes your attacks do 300 damage per hit. Since you can do 3 attacks, this means you do 900 damage. This is only useful if you're with some one else, because, for example, a Malfurion in lvl.20 will have 3685 Health, making those 900 damage kind of small. This can be changed if you land your Slime+ Pufferfish combo right before you use Octo-Grab.

Rewind- This is why you shouldn't take the Octo-Grab upgrade. I'll explain later in the guide, but in less words, do you prefer do 1300+900 (Octo-Grab) or 1300+1300 (Rewind)?

Bolt of the Storm- With Bubble Breeze and/or Bubble Machine Bolt of the Storm is kind of useless. The only use I can think of is to be able to Slime> Safety Bubble> Bolt of the Storm to run away faster.

Octo-Grab allows you to stun the enemy hero, with the upgrade you deal 900, this means you need a damage dealer with you.
If you have a friend with stuns with you, you don't need the stun from Octo-Grab, therefore you take Rewind so that you can deal more damage.

Basically you have too choose the lvl 20 talent based on your "gank friend" and the role you want to be.
If you aren't ganking, choose rewind, as it allows you to have Safety Bubble and Pufferfish always ready to cast.
Octo-Grab can also be used to counter-gank if you target the most important hero on the gank ( Diablo or Arthas).