[2.5] CWC bladefall (crit + poison) CI assassin.

> Wither as CWC channeling skill synergises really well with bladefall - it slows enemies down so they would stay in BF aoe, it boosts chaos damage dealt (and we deal tons of chaos damage), and it has high base cast speed, which is important for CWC. It's also one of the cheapest channeling skills by mana cost, making it really easy to run with 0 mana sustain incestment.
> CI is the best choice, because it means drawback-free Vaal Pact, lots of "life" for a class that has trouble getting a lot of life nodes, we get free pack size from map mods that destory life builds' natural defenses (evasion+dodge, armor+block), and you'll get to use 5 utility flasks instead of just 2-3. And it will cost you fewer passives to make, leaving more for damage passives.
And if you think that ES gear is expensive, consider that you'll make those orbs by being able to run harder maps with more quantity/packsize, and will spend less chaos rerolling those maps.
> The build can use any spell-weapon combo you want (2x daggers, dagger + death's hand, 2x wands, wand/dagger + shield), but I strongly suggest either dagger + death's hand (unholy might is extremely strong) or dagger + shield (to max ES) combos.
> The build utilises dual curse -> warlord's mark (via blasphemy) for leech + vulnerability (via witchfire brew flask) for tons of extra damage. This is optional.
> Life leech is extremely important for this build's survivability due to no other sources of damage mitigation/avoidance. As long as you're leeching - you're relatively safe.
> Getting leech enchant on boots for this reason is very important vs bosses and in long-range fights. Getting it improves the build's survivability a lot.
> The build is vulnerable to physical refect map mod due to high damage it deals, and it's also vulnerable to hexproof and no-leech mods - they can cause serious troubles for the build. Any other mods are easily doable.
> Herald of ice (only possible to run if got enlighten gem) will provide easier power charge generation via assassin ascendancy + faster trash mob clear speed thanks to those icy explosions. But only in low-mid tier maps, unfortunately. In high tier maps the added cold damage is not enough to freeze and shatter mobs on kill. If you go low life, though (see the "Gear options" part of the guide), you will be able to run extra aura (hatred) that would a allow you to deal significant cold damage at all times.
> The build will need some str + dex on gear to meet gem+gear requirements: 16 implicit roll from eye of chayula will cover the dex requirements + you will need approx 80 additional str - get it from belt and one of the rings.
> The build gets its resists from following gear: boots, gloves, armor, belt, 2x rings - just enough to cap them! Consider getting 20-30 allres from 2-3 jewels in order to run ele weakness maps comfortably.
> Can go low-life with extra investment: get shavs -> spec out of 2x passives (CI cluster) for arcane vision + pain attunenement -> drop 2x gems from cwdt links for hatred+BM (RR) for extra damage and achieving low life status.

> Triggered spell cast rate only depends on gem level => high lvl CWC is very important.
> CWC trigger countodwn begins every time channeling begins => if you started channeling, DO NOT stop channeling to switch to other targets, just move your cursor instead. Only stop channeling if you need to move yourself away from danger, or if there are no enemies left to target.
> First cwc spell trigger time = 1st channel cast/attack time + cwc gem trigger time => !!!CWC is very bad for high mobility gameplay, works best when sustained channeling is possible + stacking some attack/cast speed for channeling skill is beneficial.
>[unchecked] cwc gem trigger time is not influenced by temp chains, only the initial windup time from channeling skill.
> stun immunity is mandatory - being stunned resets both cwc AND channeling times.
> CWC is generally only beneficial to use with spells that have 0.8+ base cast speed. Faster spells can be scaled to be selfcast much faster with spell echo + cast speed, making CWC a poor choice for such spells.

This covers generally harmful map mods that may make or break a build.
> no regen = OK (mana flask + leech)
> no leech = reroll (can only use ES recharge mechanics - boss fights will make you suffer)
> reflect = reroll phys reflect (due to high damage per hit and high crit, reflect oneshots even though high es)
> enemy resistances = OK (lose some dmg from chaos res, and from enemy phys reduction mods)
> hexproof = bad, but doable (limited leech, careful around phys reflect rares and bosses, leech enchant from boots really helps here)
> ele status resistances/immunities = OK (lose some dmg from not being to proc poison 100% of the time)
> reduced flask charges gained = OK (limited flask utility)

All stats are with max power charges (6x) up, with item-based buffs active (unholy might), and no flasks active.

Bladefall dps - 21,1k tooltip average damage times 0.35 cwc trigger rate = 60.3k sustainable dps before flasks. Can easily have a 100% uptime with atzri's promise (the build uses 2x of them), and use witchfire brew for vuln aura vs bosses/big hard mobs for much higher damage dealt. Add extra strong poison on top of that.
This is on 20/20 gems. Almost all damage passives are taken though, and gear is fairy good in terms of damage-related rolls.

You can check my gear in next section, plus I took relatively few ES nodes - ES can and will easily go beyond 10k with higher investment.
Stats with spell-shield are approx +1.3k ES and approx -2k avg damage on bladefall tooltip.

My gear:



Gear detailed:
weapon = divinarius (spell dmg, spell crit, aoe) OR rare spell-dagger (!preferred ambusher base for wblades! 55+ spell dmg, 140+ spell crit, 25+ crit multi, +optional ias for faster wblades)
Can use wands instead, but will have to switch to a different movement skill then.
shield = 250+ es, 40+ spell dmg, 70+ spell crit
Can use another spell-stick or death's hand sceptre instead for more damage, if you think you have enough ES from other gear.
armour = rare es(+eva) es + res OR shavronne's wrappings(if going low-life)
helmet = the vertex (BIS, good es+eva, +1 gems for aura set up)
I'm using The Vertex because it's fairly cheap, it has great overall defenses, its +1 gems boosts Discipline, and it also boosts the lvl3 Enlighten to lvl4, which lets me run a herald on top of discipline + blasphemy curse.
enchant = any bladefall / warmark curse effect / discipline reservation / hoi reservation / any wither
gloves = rare es + res
enchant = of spite
boots = rare es + spd + res
enchant = leech if killed recently - very important!
belt = (crystal/rustic) es + str + res + flask suffix (charges gained, charges used, effect duration)
amulet = eye of chayula (BIS, stun immunity)
+1 curse corrupt is BIS, frees up 4x passives
ring1 = (diamond BIS) es + (crafted %es) + res
ring2 = (diamond BIS) es + (crafted %es) + str (to meet gem req) + res
flasks = mana (charges, anti-bleed) / atziri's promise N1 (extra phys as chaos, chaos life leech) / quicksilver (duration/charges, anti-freeze) / atziri's promise N2 / witchfire brew (extra dmg, evasion, smoke cloud) OR stibnite (duration, anti-curse/shock)
Can also use the new sin's rebirth flask as source of unholy might, and can drop mana flask for another utility flask as long as it has anti-bleed.
jewels (x6) = energy from within (near melding) / 5x %es + crit multi (spells/global) + dmg (dmg/aoe/spell/phys) + allres

Gear variations:
> The best weapon combo I prefer for myself is spell-dagger + death's hand combo. It provides a good dps increase, easy power charge sustain, and effortless 100% unholy might uptime.
> Ditching death's hand for a spell-shield will provide a good survivability boost at cost of damage ane ease of power charge generation. It's strongly advised to get sin's rebirth flask to have access to unholy might with this set-up.
> using 2x spell-daggers is also a viable combination, though it's somewhat less effective than using the default dagger + death's hand one.

Further gear and build upgrades - if you want to kick it up a notch:
> +1 curse eye of chayula will allow to spec out of 4x curse passives in favour of more ES, but will require to get some dex+str elsewhere to support gem requirements (try to get on jewels).
> Can use sin's rebirth flask as source of unholy might instead of death's hand - this allows to use another spell-stick or a spell-shield. I recommend a spell-shield for more survivability.
> Can go low-life: get shavronne's wrappings -> spec out of 2x passives (CI cluster) for arcane vision + pain attunenement -> drop 2x gems from cwdt links for hatred+BM (RR) for extra damage and achieving low life status. This will provide a significant dps boost for the build.
> If went low-life, can upgrade eye of chayula ammy to presence of chayula.

Shitty variations - I tried those and they sucked:
> The voidbringer unique gloves. They look real nice on paper with that high ES and really sweet boost to spell crit chance. Even their increased mana cost of skills doesn't hurt our CWC skill at all. BUT, that same mana cost increase mod really hurts our mana sustain when using other utility skills (totem, golem) and movement skills. That alsone makes those gloves a no-no for this particular build variant.
> Apep's rage wand. Apart from some added chaos damage and middling amount of spell damage, it doesn't really bring anything to the table. The high boost to cast speed is lost on our build because our dps mainly depends on the internal CWC trigger time that cannot be modified by anything but the gem's level (not even by temp chains, it seems). Dual apep's is a straight and significant tooltip dps loss, and then there's a significant crit chance loss that means our poison damage doesn't get doubled (via ascendancy bonus) as often, and that's another significant non-tooltip damage loss. And then there's that huge mana cost increase (see the void bringer gloves above).
> Blade flurry as CWC activator skill. It's not too bad, really. It's not really that expensive to use, it makes use of some of assassin's ascendancies that are useless for the default pure spell set-up, it hits and so it can generate extra power charges for the build. Also, as of the latest patch, the CWC trigger area has been expanded for flurry to beyond its own targeting area. So, why is this an inferior choice to wither? it's a little bit slower, and it's noticeably more expensive to cast (with my build stats: wither cast time is 0.26 and 5 mana/cast, while flurry is 0.31 cast time and 12 mana/cast). Also, using flurry means using an extra green gem, which makes rolling colours on our preferred pure ES gear that much more expensive.

This is my endgame passive tree:
It's planned up to lvl100, so you're not likely to have it all. Remove a few damage and/or ES nodes and one of 3x passive jewel sockets to get a more realistic lvl90 version.
https://www.pathofexile.com/passive-skill-tree/AAAABAYBALDYotmEojIyyBQHmRCS9W9Z8NmGaoxMjrxvFr8Pq3X9bWwki4RvNj3ndLVIwzobyNsam7UqOM_d44QQe4TF8YorCg3RvjoRL13yY0MqC_LhcFJHBtDQj_pfauwY8NVcQOv1LL_BxUlRVL3DCRXXf8ZYWhXtuZOGrpMnJ6lSKZaL8h1WY2wLvorviFXg1bki9KEvytP5N20ZtAzXzxFQ2VuX9Oq6SbE1uRslUlMNfDQKpysdT0uul5U9Xzdm6QJMsyymrrPQHyBukNZBlu_rUDDQ9dteEQ-smPfXhEiboVxrGGqPRsNteC8dFHzl-tKOZFgHZp73prcxFkByD7b6jHaFfZRvZlQ=

Leveling order and pre-CI tree:
Overall, the leveling tree looks a lot like the CI one, except you take all the life nodes along the main path instead of ES nodes.
The general leveling path (follow the passives on the passive tree linked below):
1) phys+chaos damage nodes to coordination (+take 3x life nodes).
2) go past fangs of the viper (+take 3x life nodes) towards written in blood.
3) go past CI cluster and take melding cluster.
4) go to deep wisdom at witch start (+grab 4x life and mana cluster).
5) grab the aoe cluster and go through the power charge cluster (+grab 3x life nodes nearby).
6) go towards the last power charge cluster at templar area (+grab 4x life nodes along the way).
7) fill the passive tree out with extra damage and crit nodes, and jewel slots if you feel that damage is lacking.

The passive tree you should have around level 60-65, before you are ready to respec to CI:
https://www.pathofexile.com/passive-skill-tree/AAAABAYBALDYotmEojIyyBQHmRCS9W9Z8NmGaoxMjrxvFr8mlQ-rdf1h4m1shG9VSzY9tUidqhvIbIzP3eOEYqzxig3RY0Py4UcG0NCP-l9q7Bjw1VxAwcVJUVS9f8YV7ZMnJ6mWi2wLvorviNW5IvShL_k3bRnXzxFQl_RJsTW5UlOnKx1Pl5U9X0yz0B8gbu_rUDDbXhEPrJj315uhj0YdFPrSFm9mniSq42oWQDbphX06WFXGg9uVLgceCPTAVGpDvOo=

Respeccing to CI:
You will be ready to respec to CI when you got yourself all the necessary ES gear and can meet its level requirements.
Most likely this will be around lvl68-70, though you may go CI as early as lvl62.
This is what I consider the mininum acceptable gear for CI respec: a 500+ ES 5L armor, a 250+ ES helmet, a 100+ ES gloves and boots (rainbowstrides are a decent unique boot pick), a belt and 2x rings with 40+ total ES each, eye of chayula amulet is mandatory.
It's perfectly OK to respec to CI later than that, you may want to level in dried lake some more before that.
You will use most of "free" respec points that you get from completing certain side-quests in the main game.

Here's the respec order:
1) spec out of 3x life nodes at shadow start.
2) spec out of 3x life nodes below shadow's power charge cluster.
3) spec out of 2x life+es nodes near written in blood notable (keep the notable! it gives good stats for CI).
4) spec out of 4x life+mana nodes at witch start
5) spec out of 3x life nodes near witch's power charge cluster.
6) spec out of 4x life nodes on the way to templar's power charge cluster.
You should have used 19 "free" respec points for that.
7) take CI cluster (4x passives).
8) take Vaal Pact keystone (3x passives).
9) take Ghost Reaver keystone (1x passive).
10) take 2x es+eva nodes close to shadow's power charge cluster (2x passives).
11) take 2x es+armor nodes close to templar's power charge cluster (2x passives).
12) take unnatural calm es cluster (3x passives).
13) take 4x es passives at witch's start (4x passives).
You have 1 passive point left unspent.

This is how your passive tree should look after respeccing to CI:
https://www.pathofexile.com/passive-skill-tree/AAAABAYBALDYotmEojIyyBQHmRCS9W9Z8NmGaoxMjrxvFr8Pq3X9bWwki4RvNj21SMM6G8gqOM_d44TxiisKDdERL2ND8uFHBtDQj_pfauwY8NVcQCy_wcVJUVS9Fdd_xhXthq6TJyeplotWY2wLvorviNW5IvShL_k3bRnXzxFQl_RJsTW5UlOnKx1Pl5U9X0yz0B8gbu_rUDDbXhEPrJj314RIm6Fca49Gw20dFPrSZp63MRZAjHaFfdlbGyVLrukC

After that, keep leveling and take the remaining crit clusters and ES clusters around the tree as per "final" passive tree (look at the start at this section).
The order you take them in doesn't matter much - take crit if you feel you need more damage, take ES if you want more "life".
I suggest you focus on crit clusters first, though. They will scale your damage real good, especially after you take your 2nd recommended ascendancy (see below).

Ascendancies:
> unstable infusion = 10% pcharge on non-crit. This allows the build to build up power charges. It's semi-reliable, but also using death's hand sceptre is strongly recommeded for easier sustain.
> deadly infusion = +0,5% base crit and +8% crit multi per power charge. This is what enables the crit portion of the build.
> noxious strike = useless for the build, just a pathing node unfortunately.
> toxic delivery = 10% reduced dot taken, 100% more poison damage on crits. This is an extremely strong poison boost, considering that build has 80%+ crit chance with BF in endgame.

Bandits: kill/kill/alira
With my build I killed all, so my own crit and resulting damage are actually much lower they could be.

wither(lvl1) + cast while channeling + bladefall + poison + added chaos damage + void manipulation = BBBGGG
*wither is the best channeling skill for cwc bladefall - unlimited range for triggered cwc spells (unlike blade flurry, for example), boosts chaos dmg dealt (poison!), slows enemies to keep them in bladefall's aoe and away from you, fast base cast speed.
Dont level wither beyond lvl1! Its mana cost goes up significantly, while extra levels only provide marginal increases over starting gem stats. Quality on it is nice though.
*poison is a huge non-tooltip dps boost, especially once you get your 4th ascendancy. Mandatory 5th link.
*added chaos gem is better than all other dps gems for tooltip and for utility (higher leech from atziri flask, lower reflect, bypasses enemy ES).
*void manipulation's effect on tooltip dps is fairly minor compared to other gems, but it significantly boosts your poison damage.
*crit dmg is the next best dps support once crit chance has been maxed. You may use it instead of void manipulation, if you wish - you'll get some extra tooltip damage, but you'll lose a lot of damage from poison.
*controlled destrution is ok while leveling but not nearly as good with maxed crit, unless you can overcap the gem's penalty to keep crit chance capped.
*concentrated effect is sort of bad for general clears, but can be used instead of added chaos for bosses.
*increased crit strikes is superfluous - it overcaps our endgame crit chance so much that the extra crit chance (and extra dps) is wasted; and crit damage is more important anyway.

whirling blades + faster attacks = GG - movement; put in main hand weapon
vaal discipline + vaal lightning trap + increased duration = BBR - vaal utility; put in off hand
cwdt(lvl1) + immortal call(lvl3) + vortex(lvl1) + increased duration/increased aoe = RRB(R/B) - defensive utility; IC's defensive power is undeniable, and vortex is also good thanks to slowing down of nearby mobs; put in boots or gloves
decoy totem + summon ice golem/flame golem + flame dash + faster casting = BBR(G/R) - extra offensive + defensive utility + aux movement; put in boots or gloves. Pick golem depending on your preferences, but flame golem is probably better due to its damage bonus double-dipping with poison.
warlord's mark + discipline + blasphemy + enlighten(lvl3) = BBBR - leech + extra "life"; put in helmet.
herald of ice = G - strong aoe clear assist + better pcharge sustain; put in main hand weapon with wblades. To have enough mana reservation for herald, you must put the main aura links in The Vertex (or another helmet that grants reduced mana reservation)!
+Keep Herald of Ash to swap with warmark in hexproof/no-leech maps if you decide to run those.

Most gems for the build are available to shadow class via vendors and quest rewards.
Can level either as frost blades/blade flurry melee, or as selfcast EK/blade vortex/bladefall until you got at least a 5L and a couple of ascendancies. CWC gem works best when leveled to 15+ as well.

Example of leveling progression as caster (twinked gear):
(1) lvl 1-28 - before bladefall
EK(1)->bvortex(12) + added fire(8) + added light(8)->cdestr(18) = GRB
ftrap(1) + added light(8)->ele focus(18) + added cold(8)->trap dmg(18) + cdestr(18) = GGBB
btrap(4) + added fire(8) + added cold(8)->trap dmg(18) + added light(8) = GRGB
flame totem(4) + added light(8)->ele focus(18) + fcast(18) + cdestr(18) = RBBB
wblades(10) + fdash(10) + fatks(18) = GBG
decoy totem(4) = R
clarity(10) = B
hoa(16)+hoi(16) = RG -> hatred(24) = G

leveling gear:
lifesprig x2(1) -> lifesprig+reverb rod(24) - put BV in reverb rod
wanderlust(1) -> deerstalker(22) - make BF trap with deerstalker (see below)
lochtonial caress(1)
stone of lazhwar(5)
2x any elreon rings -> 1x praxis(22) + 1x kikazaru(20)
asenath's mark(8)
briskwrap(9)
perandus blazon(16)

(2) lvl 28+ - bladefall
bladefall(28) + cdestr(18)->conc eff(18) + added fire(8)->poison(31) = GBR->GGB - put in amplify rod at lvl36
bladefall(28) + spell totem(1) + fcast(18) + cdestr(18) = GRBB
bladefall(28) + trap dmg(18) + cdestr(18) + multitrap(8)->poison(31) = GGGB - put in deerstalker
wblades(10) + fdash(U) + fatks(18) = GGB
orb of storms + increased crits + pcoc = BBB - pcharge generation
decoy totem(4) = R
clarity(10) = B
hatred(24) = G -> warmark(24) + blasphemy(31) + hoi(16) = RBG