Utility Skills for Every Assassin
The key to assassin survival are Dragon Flight, Mind Blast, and Cloak of Shadows. The first is excellent mobility, and the latter two are two of the best of crowd-control skills in the game, and you really only need one point in each. Every single assassin ever should have that 1 point, and should keep those skills hotkeyed.
The damage is practically nil, so that isn’s why you have this skill. You have this skill because it’s an almost-Teleport. Note that you do not have to select a particular enemy: if you cast it on a blank piece of ground, it’ll automatically latch on to the nearest enemy to that point.
Note that Dragon Flight is ungodly slow. It has to be used judiciously, and it is a poor escape button on its own. The next two skills are so excellent for getting yourself some breathing room, though, that it almost doesn’t matter.
(Note: the Enigma runeword can get you real Teleport. It is also a fantastic armor even ignoring that. There is almost no reason to not use this armor as any non-Sorceress, if you have access to it. This is a huge if, however, as the runes necessary for it are ridiculously rare, and the overwhelming majority of players will never see them. The runes are commonly available on Battle.net, but 99% or more of these are dupes. While they will not be detected once they are added to an armor, they are nevertheless cheating, and I strongly discourage their use.)
Mind Blast knocks enemies back, and will convert some monsters, which will cause other monsters in the group to attack them; the knockback gets monsters off of you and this infighting keeps them off of you. It can also stun, which is useful even against solo targets.
Cloak of Shadows
Cloak of Shadows, on the other hand, blinds everything on screen. This is your panic button. If you throw Cloak of Shadows up and run a little, you are no longer being attacked. This is an amazing escape button, and can let you survey the battlefield a bit to figure out which way you’re going. It’s also one of the best answers to Gloams in the game.
Note that you cannot cast Cloak of Shadows again after casting it until the first one wears off, and it does not move with you. This is a major limitation on Cloak, and a very good reason to not put more than 1 point in it (more points extends its duration, which reduces how often you can move it).
Budget Gear to Get Through Hell
Anya and the Red Portal
Assassin claws can be bought from Anya (after Act V’s Prison of Ice quest is complete), who has the convenient Red Portal next to her so you can leave town and re-enter to refresh her offerings. Bounce back and forth long enough, and you can get anything. A decent pair of Witch-hunter’s claws are awesome; Trapsins will use these (or Cunning claws) as their main weapons, and all assassins can use them on switch to pump up their precast buffs (Shadow Master, Burst of Speed, Fade, Venom). Feel free to go back to Nightmare to do this.
Circlets and coronets get bonuses when you gamble on them, and can get much better stats than other helms. Gamble on these, looking mostly for +skills and resistances. Gamble on amulets and rings, looking for the same things (except +skills on rings; only a couple of unique rings get that). If you are melee, rings can offer life/mana steal. Gambling on boots is also not a bad choice; with some luck you might score some tri-res boots, which are not bad by any means.
Runes, Runewords, and the Countess
Runewords are an extremely useful source of reliable, quality gear. The highest-level runes (those above Gul) are stupidly, fantastically rare (and, due to the fact that Hellforge caps at Gul, 99% of runes above that on Battle.net are actually dupes), but Hellforge guarantees you three runes, which in the case of Hell, can go up to Gul (including the extremely useful/valuable Ist and Um runes).
More importantly, the Countess in Act I is all-but-guaranteed to drop one or more runes every time you kill her. Hell Countess can drop up to Ist, even (actually, she can drop up to Lo, but her “special drop” that guarantees runes in much greater quantity than normal caps at Ist, so her odds of dropping higher runes is not higher than normal, that is, it’s ridiculously low). She usually doesn’t drop runes that high, but she is an excellent source of low and mid tier runes.
This is important because a number of runewords are massively helpful, yet don’t require the stupidly-rare runes. Insight (RalTirTalSol in a staff or polearm; requires level 27) is easy to farm from Nightmare Countess, and can be given to an Act II mercenary to give both of you a high-level Meditation aura, effectively eliminating your mana worries. Black (ThulIoNef in a flail or hammer) Flails make an amazing Kicksin weapon.
I strongly recommend the Treachery runeword as an amazing mid-tier armor. The Lem rune is fairly rare, but the Countess can drop Lem, and it won’t take your whole life to get one. It’s not impossible to find. Treachery hits a ton of yes points for you: +2 Assassin skills, 45% IAS, and a free L15 Fade. The latter is huge. Just remember, if you’re relying on it for resistances, that you have to activate it first. Standing in a fire (Tristram has several) is a fairly safe/easy way to trigger it.
Prior to getting Treachery, Stealth is available at level 17, gives a bunch of speed bonuses (not, sadly, IAS), and is basically my go-to for getting to Hell. Even in Hell, you can do a lot worse. Smoke is a cheap source of really solid resistances.
For melee assassins (melee anything, really), Duress is a ridiculously good armor. The Um rune is a bit harder to find than Lem, which is itself non-trivial, but if you get one, it’s a top choice. Um runes are also great things to throw in the hole you have Larzuk punch in your hat. Just please never put Um in a shield; it’s a measly 1% more resistance than the (massively cheaper and easier to get) Perfect Diamond. Save the Um for your next character, if it comes to that.
For shields, both Rhyme and Sanctuary are awesome choices (though Sanctuary’s Mal rune is about as hard as Um to find).
The primary assassin builds for PvE are trapsins and kicksins. There are others, however.
Trapsins are the easiest and safest assassin build. They are, in fact, one of the safest builds in the game (skelemancers are the only ones that are clearly safer). You gear them like casters, which relieves a lot of item requirements, and the trap mechanic means you can stay very far away from enemies if you need to while your Lightning Sentries wreck stuff.
The traditional build is 20 in Lightning, Death, and Charged Bolt Sentry, 1 in each Shadow Discipline except Venom and maybe Fade (if you choose to use Burst of Speed), and the rest of the points in Shock Web. 2 points in Mind Blast will encourage your Shadow Master to use it more often, which is a very good thing.
Trapsins usually dual-wield claws, trying to shove as many points into Lightning Sentry as possible. Treachery is a nearly-ideal armor for them. Aside from that, gambled gear can be fine.
Kicksins are devastating against solo targets, and highly mobile. They eschew the overwhelming majority of the Martial Arts tree, and merely rely on Dragon Talon to kick their foes to death. Charge-ups are not worth interrupting their devastating kicks.
For a melee build, they can be built quite cheaply, though it definitely does take some gear. In particular, you really want Gore Riders, and as an Exceptional Unique those are non-trivial to find on your own. They’re not too hard to trade for, and are a low risk of dupes. And once you get them, you really want to upgrade them to Myrmidon Greaves using the Horadric Cube, which requires a Ko, a Lem, and a Perfect Diamond; those runes aren’t exactly dropping every day (though they’re not super-rare either).
Anyway, skill-wise, the goal for a Kicksin is 18 levels in Dragon Talon after any relevant +skills. That gets you three kicks, which is what you’re looking for. Higher level is fine, of course, but probably not worth the skill points. Other than that, you’re looking at maxing your Shadow Disciplines (except, as discussed elsewhere, not Cloak of Shadows). A single point in Dragon Flight is must-have, and a single point in Death Sentry is really nice (most of its damage is based on the Life of the corpse it blows up, which makes it remarkably effective even with a single point).
Your weapon matters much, much less for kicking. It’s too much to get into the mechanics here, but the long and short of it is, damage on the weapon doesn’t matter, but its speed and other modifiers do. A Black Flail (ThulIoNef) is a really good, rather cheap choice. Crushflange (the unique mace) is also a solid, super-cheap choice. Even among the stupidly super-rare runewords, it’s hard to beat that Black Flail. The idea, though, is Stormlash (the rarer of the two unique scourges).
Duress is your best armor, Treachery is a solid interim.
For shield, Rhyme (ShaelEth) is your budget option. With Cannot Be Frozen, unless you get a Ravenfrost, it might be your best option. With a Ravenfrost, you’d really like a Stormshield (unique monarch); if you get one, have Larzuk punch a hole in it and include a Perfect Diamond. Whitstan’s Guard (set round shield) or Santuary (KoKoMal) are also good choices.
Make absolutely sure you have Life Steal on you. You hit hard and fast enough that even a small amount of it will go a long way. Top tier is, like it is for most melee, Dracul’s Grasp.
The dancer is a hybrid kick/trap-sin. Basically, you skill-up like a Trapsin, except you get enough skill points in Dragon Talon to hit 18 after +skills. You gear up like a kicker. Your traps hit hard, though not as devastatingly as a true Trapsin&rsqou;s, and you hit ridiculously hard as well.
The dancer is one of the most versatile builds in the game. It is also almost certainly the one most naturally suited to key and organ runs (though the Smiter is massively better in Uber Tristram itself).
Using the Martial Arts skills is... frustrating in the extreme. The problem becomes fairly obvious if you think of it like this: you effectively cut your attack speed to one quarter what it would otherwise be by using them, because only every fourth attack actually gets the advantage of your skills.
The best ones are Tiger Strike with Dragon Tail, and Phoenix Strike. These are two separate builds that don’t overlap with one another.
Tiger Strike + Dragon Tail works because the damage of Dragon Tail’s explosion is based on your physical damage, so you effectively hit multiple people with your Tiger Claw charge-ups when it explodes. It’s not great, really limited in damage types (physical and fire are your only real options), small radius, and so on, but it can be done.
Phoenix Strike has the primary advantage that you can release a single charge, and get a powerful effect (a meteor). That way, your attack speed is halved, rather than quartered. Furthermore, you have other damage types available if you need them. It works... OK. For finisher, most just use a regular attack; phoenix strikers are incredibly strapped for skill points because of all the prerequisites and synergies that Phoenix Strike has. It also helps your timing: using Phoenix Strike relies on being able to alternate attacks at high speed with enough accuracy that you’re able to drop the effect you want as often as you can. Focus on the fire synergy, and either the lightning or the cold; the cold is usually easier to get the timing right. You still want the usual 1-point-wonders (Mind Blast, Cloak of Shadows, Shadow Master, Death Sentry). Note that Phoenix Strike does not use dual-wielding and as such you are strongly recommended to use a shield.
This assassin relies on Shadow Discipline skills. Dragon Flight is used for mobility, and Death Sentry for solid, cheap AoE damage, but most of the build relies on Mind Blast, Claw Mastery, Weapon Block, and Venom, along with Fade or Burst of Speed (or Shadow Master and rely on Treachery for Fade). Not, by any stretch of the imagination, a high-power build, since your primary attack is just a normal attack with Venom on it.
If you manage a Chaos, though, it does turn nicely into a solid whirlysin build. That’s more PvP than PvE, but it can PvE fairly well.