Guide written by Icebird on the DiabloII.Net Single Player Forums.
This guide is designed as an introduction to the Assassin from a Single Player perpective. It provides an overview of sone of the most commonly used Assassin skills, outlines of a few common builds and some equipment advice. More detailed information can be found in the guides in the Strategy Compendium. This guide is based on the skills and equipment available in the 1.09 Diablo II patch.
The assassin skills allow you to fight up and close and personal with martial arts, or hang back and let your traps do the damage, or combine the two approaches depending on what monsters you face. There are three broad ways to play an assassin:
Due to the limited number of skillpoints, a martial artist or hybrid will rarely invest the maximum number of skillpoints in more than one trap, whereas the pure trapper will usually seek to raise two or more traps to maximum level.
Like barbarians, assassins can wield claw-class weapons in both hands. There are advantages and disadvantages to dual wielding.
A shield is more defensive. Achieving high resists is easier with a shield, and you can achieve higher blocking with a shield than with weapon block.
Using two claws, certain attacks (Dragon Claw, Fists of Fire, Claws of Thunder, Blades of Ice) will strike faster than when using only one claw. (Dragon Claw can *only* be used when dual wielding). Some claws give bonuses to assassin skills. Many trappers choose to dual wield simply for the additional skill bonuses
More than any other class in the game, playing an assassin requires extensive switching between skills. You might use up to six or seven skills in a single fight. For that reason, finding a comfortable hotkey set-up is crucial. If you haven't done so already, I recommend switching your skill selection keys away from the default F1-F8 configuration. In my set-up, skills are assigned to keys A through J, and Z through N, with the most often used skills assigned to A, S, D and F. Effective assassin play requires you to comfortably and continously cycle through the skills.
The martial arts skills are divided into "charge-up" moves and "finishers". Charge-ups are shown on screen as coloured balls orbiting your assassin. Each time your assassin lands a successful strike with a charge-up move, a coloured ball will appear. Each charge-up move can be charged up to three times. As long as you continue to land a charge-up move within six seconds or so of your last hit, the charge-ups will persist until you release them with a finisher or with a normal attack. Multiple skills can be charged up at once, and the effect of all charge-ups will take effect when the charges are released. For example, Tiger Strike can be combined with Cobra Strike to increase the damage you leech back from.
Tiger Strike, Cobra Strike and Phoenix Strike only use the claw in the primary hand, even when dual wielding. These attacks can be used when wielding a non-claw weapon.
Tiger Strike: Increases the damage of your finishing attack. Useful even at level 1, at high levels this skill increases your physical damage by a huge amount. One popular martial arts build uses Tiger Strike in combination with Dragon Tail.
Cobra Strike: The assassin's all purpose leeching tool. One point is usually enough, since it is often more effective to increase the damage you do in the first place than increasing your leech. This skill is most useful at low levels, when you may not have any leech from your equipment.
Phoenix Strike: An elemental triple-threat. If you charge up once, then release, a meteor will appear to strike the target. Charge up twice and release, and a chain lightning type attack will hit every monster within range. Charge up three times, and the attack releases a swirl of ice bolts. These icebolts freeze every monster they hit, and the freezing time appears to gain duration with more skill points. The freezing bolts are one of the premier crowd control tactics the assassin has. Lister and his minions of destruction are surprisingly easy to defeat when frozen solid. (Note: "boss" monsters like uniques and superuniques will only be slowed, not frozen).
Of the three "elemental" martial arts attacks, "Claws of Thunder" is only the one used extensively.
Claws of Thunder: This adds a lightning attack to your finsher. Charging up once and releasing adds lightning damage to your claw. Charging up twice releases a nova attack. Charging up three times releases 16 charged bolts in a circle around the assassin. At high levels this skill can add a lot of lightning damage to your attacks.
Charge-ups can be released using a normal attack, or special "finishing move". Most of the finishing moves are kicks. Kick damage is based on strength and dexterity, with a mininum damage calculated by (STR+DEX)/4 and a maximum damage calculated by (STR+DEX)/3. Finishers can be used at any time, whether any charge-ups are active or not.
Dragon Talon: Kicks twice, or at higher levels, 3 times. The charge-ups are released on the first kick.
Dragon Claw: A quick double-claw attack.
Dragon Tail: This attack converts the physical damage of your kick into fire damage and applies to all monsters within a four foot radius. It also knocks all the monsters in the splash radius back. The attack can be useful against PIs with one caveat: The monster you kick cannot be Physically Immune - since your kick would no damage, nothing would be converted into fire damage. This skill is most often combined with Tiger Strike to increase the physical damage the kick does.
Dragon Flight: The assassin will teleport and kick a target. One point is useful in this skill for mobility purposes. You must have a target to use this skill and there is a "casting delay" limiting you from teleporting rapidly in succession. You can use your shadow as a valid target. Hold the pointer over the Shadow with Unsummon as your left-hand skill and use Dragon Flight as your right-hand skill.
Listed below are the three most commonly used assassin traps, plus another skill in the trap tree useful in some situations. Traps are placed on the ground, where they will automatically target any enemies within range. You can have up to 5 traps active at one time. If you cast another trap after that, one trap will vanish. You can several different types of trap active at any one time. Traps will remain active until you lay more traps, or they use up their "charges".
Wake of Inferno: The effect is similar to the sorceress' Inferno skill. A jet of fire will burn targets. Wake of Inferno has a short range, and may have difficulty targeting fast-moving targets. It does the most damage of any trap. This trap is best used against tightly packed groups, and slow-moving solo targets.
Lightning Sentry: Shoots lightning bolts at the enemy. This trap does less damage than Wake of Infero but has a greater range, and copes better with fast-moving targets. Useful for dealing with scattered groups of enemies.
Death Sentry: This trap has two effects. It will shoot lightning bolts which are similar (but less powerful) than the bolts of Lightning Sentry. It will also blow up dead bodies like the necromancer's Corpse Explosion skill. The corpse explosion radius is small at low levels. Adding points increases the lightning damage and the radius of the corpse explosions.
Blade Shield: This skill works differently from the skills above. When cast, a rotating shield of blades will surround your assassin. The shield will do damage to all monsters within range. The damage done by Blade Shield is small but it has certain useful properties. If you are wearing equipment that causes an effect when a monster is struck, the blade shield will share those properties. Examples include: Hit Freezes Target, Hit Causes Monster to Flee, Deadly Strike, Crushing Blow and "chance to cast" effects such as Amplify Damage. Blade Shield has shown to be particularly effective when combined with equipment that gives a high crushing blow percentage. Blade Shield is affected by weapon range. A range 5 weapon such as a pike will effect more monsters than a range 1 weapon such as assassin claws. There also seems to be a relationship between weapon range and attack speed, with blade shield appearing to hit more frequently with shorter range weapons. The duration of Blade Shield is quite short. Except at high levels you will have to recast it reaonably frequently.
The Shadow Discplines skill tab contains a number of useful support skills for the Assassin.
Claw Mastery: Similar to the Barbarian masteries, this skill increases your damage and attack rating. It also shares the critical hit bug of the barbarian masteries (1 point will give you a 100% chance of critical strike). This is where you should invest your first skill point.
Burst of Speed: The Assassin has 3 abilities similar to paladin auras or barbarian warcries. Only one can be active at any one time, and they don't share bonuses with party members. Once cast you can switch to other skills. Burst of Speed increases both your running speed and attack speed. The attack speed bonus is similar to the bonus from the paladin's fanatacism aura. The other similar skills are FADE, which increases resistances, and VENOM, which adds poison damage to your weapon. Resistances are easier to get on equipment that attack speed, so most players opt for Burst of Speed. Venom is generally only used by variant builds specialising in poison attacks.
Weapon Block: When dual-wielding claws, this skill allows you to block attacks. The block percentage is fixed, unlike shield blocking which varies depending on your dexterity. A few points here can be useful if using two claws.
Cloak of Shadows: An instant "Dim Vision" skill. This is especially useful against ranged attackers, and will also stop shamans and mummies from ressurecting monsters. This skill can also aid escapes from tricky situations. Cloak of Shadows does not need to be targeted and has a large range.
Mind Blast: A skill with numerous uses. Mind Blast stuns all monsters within its radius of effect, and has a chance to convert some monsters to temporarily fight by your side. Along with the Phoenix Strike ice bolts, this is the assassin's primary crowd control tool. Converting monsters can instantly give you a few extra meat shields to absorb the brunt of monsters attacks. The conversion effect works well against boss packs. Converted minions can kill themselves attacking their lightning-enchanted leader, or get themselves cursed, making them easier for you to kill. Even the stun effect has uses. Mind Blast can be used to prevent monsters such as Zakarumites and Oblivion Knights from running away, and Mind Blast can stop the Act V suicide minions in their tracks, allowing them to safely destroyed by your mercenary, Shadow or traps.
Shadow Warrior and Shadow Master: The Assassin has two summonable minions to call upon. Only one can be active at a time. The Shadow Warrior will use the two skills you currently have selected. This allows you to control what skills the Shadow uses - forcing them to lay traps for instance. The Shadow Master can (and will) use all of the assassin skills except for Shadow Warrior and Shadow Master. If you use Shadow Master extensively, you should get accustomed to the frequent use of Cloak of Shadows and Mind Blast by the Shadow. Shadow Master gains resistances as more points are invested, and is quite durable at high levels. Trapping assassins usually invest maximum points in a Shadow to act as a "tank" to hold monsters in place while the assassin lays the traps.
Martial arts assassins and trappers have slightly different equipment needs. Martial artists are involved in the thick of battle, and share many of the same equipment needs as other melee classes: a damaging weapon, resists, bonuses to skills and stats. Pure trappers will typically hang back from the action, so they will usually aim for getting the most bonuses to skills, sometimes at the expense of resists or damage.
There are only two "named" claws that the assassin can use. Natalya's Mark is the set Scissors Suwayyah. It offers high physical damage and good attack speed. However you must be level 79 to use it, and in the single player world, this item is both hard to find and expensive to trade for.
The other claw is Bartuc's Cut Throat, the unique Greater Talons. These claws offer a variety of mods useful to both martial artists and trappers. The claws do good damage, attack fast, and add +2 to assassin skills plus an additional +1 to martial arts. The claws also add an attack rating bonus, life leech, faster hit recovery and large additions to both strength and dexterity. Best yet, the assassin can use one in each hand, doubling the bonuses. These are excellent "end-game" claws. They are exceptional weapons, and can be dropped by Mephisto in Nightmare.
For magic or rare claws, martial artists tend to look for the most damage possible (such as a cruel elite claw), while for trappers, bonuses to skills (to incease trap damage) are usually the paramount concern. Claws can have a maxium of 3 sockets, limiting the number of the useful weapon runewords for assassins. "Malice" and "Strength" can be used at low-levels.
There are a variety of useful mods to look for on the equipment that fills the rest of your equipment slots: Life and mana leech, resists, physical damage reduction, Cannot Be Frozen, +skills, +stats (especially if you use kicks extensively). With 6-10 points invested in Burst of Speed assassins usually don't need much Increased Attack Speed, with 20% or so often being enough to achieve the fastest attack possible.
Much of the information here is compiled from material on DiabloII.net, guides in the Strategy Compendium and posts from the Assassin Forum. You can use these sources for more detailed information on playing particular types of assassins.