[3.17] Ice Spear League Starter (SSF friendly)

https://pastebin.com/pC09MQMW
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I have removed almost all the gear, flasks and jewels from this PoB. The point is to let you fill it up yourself with gear that is attainable for you and not present unrealistic numbers. The Gear section has some ideas for what to fill it up with.

Although it is not in the PoB, you can optionally take Righteous Decree in the Templar area for an extra 2 points if you are having mana problems.

(6L) Ice Spear + Increased Critical Strikes + Increased Critical Damage + Unleash + (flexi) + (flexi)

Ice Spear: The star of the show. Ice Spear's hitbox is narrow but reaches extremely far.
Increased Critical Strikes and Increased Critical Damage: Ice Spear already has crit chance and crit damage built into its second form, which is why I decided to make a crit build from it. Cold crits also freeze and shatter mobs.
Unleash: As a ranged projectile build, you will be moving around a lot and casting a bunch of other support spells. Any moment you aren't casting your main damage spell is a DPS loss... unless you have Unleash, which allows you to lay out your damage in measured bursts instead.

There's a lot of flexibility in the last two gems, but I will list some good options roughly in order of how useful I think they are.
Volley: Volley makes the hitbox of your Unleash cast a lot wider and is by far the best support for general clearing. You can go with Greater Volley if you want but I personally feel Volley is just right.
Pierce: Good for situations with high melee mob density: Delve, Incursion, bosses with annoying melee minions, etc. Pierce makes this build much better at situations where you can be easily overwhelmed in melee like Ritual and Delirium, at the cost of sacrificing DPS.
Added Cold Damage, Hypothermia: Higher base damage also gives higher freeze duration.
Lesser Multiple Projectiles, Greater Multiple Projectiles: More dakka.
Elemental Focus: The best option for pure DPS but sacrifices freeze and shatter.
Inspiration: If you need the reduced mana cost, or if your 6L has a red socket.

I am personally running:
Volley + ACD for mapping
Volley + Pierce for Delving
LMP + ACD for bosses
LMP + Pierce for bosses with SRS-like minions

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(4L) Power Siphon + Chain + Hextouch + Frostbite/Temporal Chains
OR
(4L) Power Siphon + Power Charge on Critical + Increased Critical Strikes + Blind

Power Siphon: Lots of projectiles and Culling Strike built in, and gives power charges (which increase crit chance!).
Hextouch + Frostbite/Temporal Chains: Frostbite is the most useful and you will probably be using this until you get a Frostbite ring. After you get a Frostbite ring and Malediction (ascendancy, gives additional curse), you can swap Frostbite for Temporal Chains (or any other curse you prefer using, really).
Chain: Extends curses to the whole pack of mobs. This is especially important for the explode from Profane Bloom (ascendancy, cursed enemies have 40% chance to explode on death).

Power Charge on Critical + Increased Critical Strikes + Blind: Alternate general utility setup if you already have a Frostbite ring but don't want to use another curse. PCoC and Crit Strikes together give power charges much more reliably than Power Siphon alone. Blind is extra safety and can be swapped for something else if you prefer.

If you'd rather hand cast your curses, or don't want to use a wand, you can go with Frostbite/Temporal Chains + Increased Area + Intensify or something along those lines instead.

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(3S) Zealotry/Hatred, Herald of Ice, Summon Skitterbots

Zealotry/Hatred: Damage, sweet damage.
Herald of Ice: You will be shattering a lot of enemies, so this combos nicely with the explode from Profane Bloom.
Summon Skitterbots: Applies chill and shock and you don't even have to lift a finger. The chill is especially important for the freeze from Frigid Wake (ascendancy, periodically freezes enemies which are chilled). They also run towards the nearest mobs of their own accord, so if I see my skitters run ahead I know there are mobs in that direction (and then I can Power Siphon-Ice Spear in that direction to offscreen them).

The default mana reservation of these is 50% + 25% + 35% = 110%, so I included some mana reservation efficiency on the tree, but you can adjust this based on your mana.

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(4L) Summon Reaper + Summon Skeletons + Meat Shield + Minion Life

You might be wondering, why include minions in a caster build? One major downside of Ice Spear is that it is practically useless in melee range, so you'll want to remain at arm's length from the thing you're casting at. That's where Meat Shield's taunt comes in - you need something to be able to stop melee mobs (rares especially) from running at your face all the time so you can distance yourself to cast Ice Spear. I like Summon Reaper for this purpose because it can be reactivated to target a certain area/enemy. Summon Skeletons can be spammed and also serve as Reaper food. Minion Life just lets them tank longer.

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(3L) Frost Bomb + Frostblink + Arcane Surge/Second Wind

Frost Bomb: A must have for the cold exposure.
Frostblink: My personal preference due to the assorted Cold skill scalings in this build, although you can certainly substitute Flame Dash, Shield Charge, or whatever movement skill you prefer.
Arcane Surge: Some extra mana regen and spell damage. You can keep the level low to trigger a smaller effect more often, or level it up to trigger a larger effect less often, as you prefer.
Second Wind: If you want extra charges in exchange for a longer cooldown.

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(4L) Cast when Damage Taken + Steelskin + (flexi) + (flexi)

Again, there's a lot of flexibility in what you want to CWDT.
Steelskin: the best Guard skill option for a build with high mana reservation, little armour and no endurance charges.
Vortex: Chills an area which helps with mob control, and some extra damage.
Cold Snap: Similar to Vortex, less damage but gives Frenzy charges, and it also triggers where your mouse is at instead of at your feet.
Summon Flame Golem, Summon Lightning Golem, Summon Chaos Golem: Flame or Lightning for damage, or Chaos for PDR if you feel squishy.
Hydrosphere: A bit of extra damage and cold exposure.

Optional if playing SSF.

Light of Lunaris shield [link]
Easily the BiS shield for this build, gives a ton of stats that we need.

Crown of the Inward Eye helmet [link]
Transfiguration of Soul and Transfiguration of Mind will constitute a good chunk of your DPS.

(If you can't find a Crown with an Ice Spear lab enchant, it's almost always better to use an unenchanted Crown than a rare helmet with an enchant.)

Look out for the following mods:
Wand: +1 to Level of all Cold Spell Skill Gems
Gloves: % increased Spell Damage (Fingerless Gloves)
Boots: at least 25% Movement Speed
Amulet: +1 to Level of all Cold Skill Gems
Ring: Curse Enemies with Frostbite on Hit

Helmet (only if not using Crown of the Inward Eye): Skills supported by Unleash have +1 to maximum number of Seals

For the other mods, the most important stuff is Resistances > Life > ES > attributes (Str and Int are both useful for buffing life and ES respectively, while a bit of Dex is necessary to meet gem requirements)

Anoint: flexible depending on what you need
DPS: Divine Judgement, Heart of Ice
Life: Heart of the Warrior, Constitution
ES: Arcane Focus, Unnatural Calm
Block: Deflection, Sanctuary
Other interesting stuff: Longshot, Quickstep, Disciple of the Slaughter, Disciple of the Forbidden

Jewels: max life, max ES, crit dmg, +cold dmg to spells

Optional if playing SSF.

Large: Seal Mender and any two out of Burden Projection, Conjured Wall, Essence Rush, Mage Hunter, Thaumophage.

Medium: Any two out of Aerodynamics, Eye to Eye, Streamlined, Repeater

Small: Sublime Sensation

Ascendancy order:
1. Void Beacon
2. Frigid Wake - a ton of safety with cannot be chilled/frozen and free freezes in conjunction with Skitterbots
3. Profane Bloom - explode makes your clear smooth as butter for mapping
4. Malediction - extra safety (with Temporal Chains) and 10% increased dmg

If you don't want to play Occultist, then Elementalist, Assassin, and Inquisitor are also viable alternatives.

Bandits: Alira or Kill All

Pantheon: flexible, although my personal preference is for Lunaris and Ryslatha.