Pitted against the very society that condemned her to a life of Undeath, Mortred takes delight in the slaughter of her kindred people. Abandoned during their expeditious retreat in battle, she was left to the mercy of the undead. Her wisted fate was merely a sacrifice to them - a tool in slowing their predators' pursuit. But... the Lich King saw the malevolence and hatred within Mortred. He bestowed upon her an opportunity - a vessel of darkness with which to enact her vengeance. Eternally grateful of his service, Mortred hunts her wretched Night Elf sisters from the shadows, fueled by an insatiable desire to seek her form of justice.

This little guide is assuming you already know a little bit about the Phantom Assassin from Defense of the Ancients. We're only going to go into some items you might want to include in your builds and opinions of them. You can see this Mortred guide for how to play her during a DOTA match.

• Lifesteal: A popular choice, but not good unless you're planning on demolishing the enemy team with the phantom assassin alone. You'd benefit much more from adding items that help you deal even higher DPS.
• Battlefury: This item is potentially great. However, it depends on your playstyle. The key to using it correctly is NOT attacking your target. If there's a creep near them, hit that instead! The splash damage is unreduced, and absolutely devastating if you land a critical hit. Of course, if you go with armor reduction items, you can just hit the heroes for maximum damage.
  
• Maelstrom: A poor item originally, it becomes useful with the updated Phantom Strike ability. This will give you an extra 100% attack speed for 3 out of every 5 seconds. In other words, your chain lightning will be landing often! You probably shouldn't upgrade it to Mjollnir unless the game is both EM and has reached the final stages. The hammer upgrade only adds a bit more damage to the spell, an agility boost, and an ability that's not useful unless you have someone else tanking.
• Stygian Desolator: My favorite orb on her, especially mixed with an assault cuirass. Lowering the armor of enemies by 10 points, mixed with Mortred the Phantom Assassin's devastating DOTA critical hits... ouch!!! If you really, really want lifesteal, grab a Vlad's too.
  
• Shiva's Guard: A complete waste on her. You don't need the extra mana, and the slow/nuke isn't necessary. Use your stifling dagger and phantom strikes to reach the enemy in time to kill them.
• Cranium Basher: It used to be a bad choice, but it works decently well now. Phantom Strike will allow you to critical often. Between the bashes, stifling dagger, and your blink, enemies won't be able to run away during team fights.
• Black King Bar: A BKB is extremely useful if the enemy has been trying to disable you. And they should! The phantom assassin is fairly useless should the enemy take you out of commission. This little baby will let you use avatar and become magic resistant. It only lasts 5 seconds after a few item uses, but that could be enough to destroy an entire team.
• Monkey King Bar: More attack speed. Ignores evasion (if you don't have other orb effects). Ministuns that stop any channeling spells or teleports away. Get one, enough said.
• The Butterfly: A popular choice, but not really a good one for the Phantom Assassin. This dota hero has a skill which gives her enough evasion to equal the bonuses given by the sword. No need for it. Grab other DPS items instead, and a hyperstone or cuirass for your attack speed.