While the skill and item builds in this guide are universally applicable to any level of play, some of the advice and strategies mentioned are not. Most of the people who don't know how to play DotA play public games, so this guide is primarily a pub guide. However, I'll do my best to make this guide at least partially worthwhile for all levels of play.

Hero role:
Phantom Assassin is a hard carry. That means her role on a team is to farm up early game so she can deal major damage in lategame teambattles. An underfarmed or underleveled PA is useless to her team, so you should prioritize farming and leveling over anything else.


I recommend the following Skill build:


Your core build should look something like this:
Game Walkthrough
Starting items:
These items give some survival in lane, some extra last-hitting power and they go into Poor Man's Shield and Magic Wand.

Alternative:
This gives you slightly more hp and mana for a safer laning phase, at the cost of attack damage and easy item assembly.


Go to the long lane (Bottom Sentinel, Top Scourge), preferably with a ranged babysitter and lane passively. Your focus should be last-hitting and gaining experience, not harassing. Use Stifling Dagger to last-hit creeps. If you can't farm a quick Ring of Health, get a Magic Stick/magic Wand and a Poor Man's Shield to mitigate the harassment. If you have a good ally (with a good hero), you'll be able to get kills pretty early if your opponent screws up, so pay attention to opportunities. If your opponent stays behind while his creeps are almost all dead, Stifling dagger, Phantom Strike and a disable from your allies will probably be enough to make a kill. The range on both Phantom Strike and Stifling Dagger is far greater than that of most spells, so you'll be able to attack heroes that believe themselves to be outside of reach.


If you can't farm in your lane, either because your ally sucks or because your opponents are too strong, try to farm neutral creeps. Buy a Mask of Death and perform some creeppulls to speed up your initial jungling. Your objective is still to farm up a fast Battlefury, so don't go overboard buying all sorts of lifesteal. If you don't need it, it's delaying your battlefury.

These should only be gotten if necessary. Never get lifesteal early if you're laning. When last-hitting, the regen provided from Lifesteal will be minimal, and since it doesn't stack with Quelling Blade you'll lose last-hitting power too.
In lane, the regular hp regeneration from your Ring of Health and Tango's should be enough, if not, either go jungle or get a Helm of Iron Will .
Mask of Death can later to be turned into Helm of the Dominator / Mask of Madness / Vladmir's Offering.
NOTE: Vladmir's Offering works with Quelling Blade

Once you get your Battlefury, your farming speed should increase to the point where you can farm your PT/BKB in the next 15-20 minutes. You should start participating in teambattles, albeit carefully. Until you get your BKB, you're still fragile as heck. Once you do have your core items, it should be pretty much game over for your opponents.


Luxuries
If the game doesn't end shortly after acquiring your core items, you should focus on getting more hp, and then just stack on damage.



Stifling Dagger
Hurls a dagger which deals minor pure damage and slows the unit's movement speed for a short duration. Deals half damage to heroes.
Cooldown: 10
Manacost: 30/25/20/15
Level 1 - 40 Damage, 50% Slow. Lasts 1 seconds.
Level 2 - 80 Damage, 50% Slow. Lasts 2 seconds.
Level 3 - 120 Damage, 50% Slow. Lasts 3 seconds.
Level 4 - 160 Damage, 50% Slow. Lasts 4 seconds.

This skill has three uses:

- Last-hitting creeps. This is arguably the most important aspect of the skill. With it's low cooldown and manacost and it's enormous damage against creeps, this skill allows you to safely last-hit from a great distance.
- Slowing enemy heroes. Do I need to explain this?
- Vision. Stifling Dagger grants vision of the area it passes through for a couple of seconds. Very useful against juking enemies, provided they don't cancel your spell by moving into FoW before you finish casting it.

NOTE: Do NOT use this skill to "harass" enemies. 80 damage every 10 seconds is pathetic, and you're just wasting creepkilling opportunities. If you can get significant damage out of Dagger+Strike then do so, because lanecontrol means more farm for you. If you have no hope of scaring away your opponent, then don't bother trying, especially not with Stifling Dagger spam. A clever opponent will get Magic stick against Mortred, so then spamming your spells on him will give him free mana with which to rape you.


Phantom Strike
Teleports to a unit and attacks it. Gains 100% attack speed for 3 seconds while attacking that same target. Maximum of 4 attacks. Casting range improves per level.
Cooldown: 30/20/10/5
Manacost: 50
Level 1 - 700 Range.
Level 2 - 800 Range.
Level 3 - 900 Range.
Level 4 - 1000 Range.

This skill is useful for many different things. Mastering Phantom Strike's many uses is very important in becoming a good PA player. It can be used to:

- Last hit creeps. Just like Stifling Dagger, Blink Strike is also a useful last-hitting tool (it brings you into last-hit range faster than walking). The downside is obviously the higher manacost and the fact that it brings you close to the enemy, where you can get hit by spells/attacks.
- Chase heroes. No brainer, just spam Phantom Strike on a fleeing hero and he won't get away.
- Escape. This is probably the most tricky aspect of Phantom Strike, because it requires you to anticipate other units' movements as well as your opponents' reactions. The trick is to Phantom Strike as far away as possible from your opponents, or when that's not possible, to confuse them by Blinking in an unexpected direction and then hiding.

NOTE: Phantom Strike cannot be used to dodge projectile spells (Hellfire Blast&co). Even if you time your blink perfectly, you'll just be stunned/nuked at the point of arrival.


Blur
The Phantom Assassin becomes hard to see by blurring her body. Some enemy attacks miss. Mortred's hero model becomes more difficult to see with each level.
Passive
Level 1 - 15% dodge.
Level 2 - 20% dodge.
Level 3 - 25% dodge.
Level 4 - 30% dodge.

- The Evasion from this skill does not stack with the Evasion granted by Butterfly/Talisman of Evasion.
- The Transparency effect is purely cosmetic. It still allows your enemies to see you and target you. It just makes you a bit more difficult to spot.

Coup de Grace
Mortred has refined her hero-killing skills to a high degree.
Passive
Level 1 - 15% chance to 2.0x critical.
Level 2 - 15% chance to 3.0x critical.
Level 3 - 15% chance to 4.0x critical.

This skill works like any other Critical Strike skill.

- Mathematically, this skill provides a 15% / 30% / 45% increase in your average damage.
- It does not stack with Crystalis/Buriza-Do Kyanon. If both criticals would occur on the same attack, the last critical acquired (typically Buriza) will override the other.
- Bonus damage effects such as bashes (Basher, MKB), Chain Lightning (Maelstrom/Mjollnir) and Feedback (Diffusal Blade/Manta Style) are not calculated into the critical strike damage.
- Lifesteal and Cleave work with Coup de Grace.

When you want to chase someone, you should cast Stifling Dagger first, and immmediately cast Phantom Strike on the same target. This way, you can attack for the full duration of the attack speed buff from Phantom Strike (if you cast Dagger after Strike, you lose some time because of Dagger's casting animation; if you cast Dagger but don't Strike immediately, you waste some of your precious slow's duration).


Never be the first one to go in unless you have a BKB, and even then, do so with caution: there are plenty of spells that'll disable you through BKB. Try to assess which hero is the poses the biggest threat and focus him. When in doubt, focus on low-armored (and perferably low-hp) heroes as these go down fastest and allow you to cleave the most damage.