
HP: 1365
HP Regen: 2.8437/s (487.5~ seconds to reach max)
Damage: 60
Attack Speed: 1/s (1 second cooldown)
Attack Range: 5.5
Unit Radius: 0.625
Trait

Frostbite
Jaina's Abilities all apply 'Chilled' to affected enemies for up to 4 seconds past last application, as well as a -25% Slow that also lasts up to 4 seconds past last application. All of Jaina's damaging Abilities (But not her Basic Attacks) add 50% of their base damage to their final damage against Chilled enemies.
Note that the Chilled status is somewhat disconnected from its Slow. Unstoppable targets will become Chilled but not Slowed, including that if the Unstoppable ends before the Chilled status the Slow won't kick in at that point. Similarly, a few Heroes can pretty specifically cleanse a Slow, which won't remove the Chilled status, and when the 'Relentless' mechanic applies it will cause the Slow to go away early but not the Chilled status. (eg Alextraza in Dragonqueen will have the Slow end in 2 seconds, but Chilled will still last 4 seconds)
Friendly Stasis and Invulnerable are notable exceptions that will cleanse both the Slow and the Chilled status.
Chilled itself is communicated two ways: firstly, Jaina's player can see a snowflake icon underneath the HP meter of enemy Heroes affected by Chilled. Second, everything affected by Chilled has visual effects applied to their 3D model of an icy haze and little snowflakes; these effects are visible to all players, though they're unfortunately a bit easy to overlook in real play.
jaina's trait involves talking about movement mechanics (non-heroes can be faster/slower with the stat box not communicating this, Erik is faster with same issue, etc) plus 'default' behavior leading to easy disengages -and jaina's trait screwing with this, even though jaina herself otherwise cleaves to these defaults and actually has zero mobility-enhancing tools prior to Level 20
Q Slot

Frostbolt
Mana: 30
Cooldown: 4 seconds
Windup: 0.125 seconds
Fires a 1.6-long and 1-wide Skillshot projectile in the chosen direction, traveling at speed 15 out to up to range 10.5. The first enemy it hits takes 184 damage and becomes Chilled, while the projectile terminates.
Chilled bonus damage: 92
W Slot

Blizzard
Mana: 90
Cooldown: 15 seconds
Windup: Instant
Recovery: 0.1 seconds
Targets a radius 2.5 area whose center is within range 7. After 0.75 seconds, damages and Chills all enemies in the area, repeating after 1.25 seconds and again 1.25 seconds after that. Each wave does 142 damage per target.
Chilled bonus damage: 71 (Per wave per target)
code says 0.5 second initial delay
E Slot

Cone of Cold
Mana: 40
Cooldown: 10 seconds
Windup: 0.125 seconds
All enemies in a 45 degree cone with a radius of 7 in the chosen direction take 220 damage and are Chilled.
Chilled bonus damage: 110 (Per target)
Heroic 1

Ring of Frost
Mana: 70
Cooldown: 70 seconds
Windup: Instant
Recovery: 0.1 seconds
Targets a ring-shaped area whose center is within range 9. After 1.5 seconds, all enemies touching the ring are Rooted for 3 seconds, take 310 damage, and become Chilled. For 3 seconds after impact, Chills enemies that touch the ring. The ring's inner radius is 2.6 and its outer radius is 4.5.
Chilled bonus damage: 155 (Per target)
code seems to imply more generous range for hitting Structures; 1.75-4.75
Heroic 2


Summon Water Elemental
Mana: 60
Cooldown: 60 seconds
Windup: Instant
Recovery: 0.25 seconds
Summons a Water Elemental at a targeted location within range 8, which lasts up to 20 seconds, and takes 0.85 seconds to become able to act. The Water Elemental attacks once per second for 62 damage, has 958 base HP, has a unit radius of 0.375, moves somewhat faster than base Hero movement speed (5.1992 vs 4.8398), has an attack range of 5.5, and a sight radius of 7. Its attacks 'splash', hitting all enemies within radius 2 of the primary target, but the splash damage hits have a base damage of 15.5, and its Basic Attacks apply the Chilled status and benefit from it. The Water Elemental will autonomously attack enemies if not given orders, and can be ordered to move to locations or target specific enemies through use of the Heroic Ability button. The Water Elemental has a leash range of 15; it cannot move further than that from Jaina, and if she moves so the leash range is exceeded it will move toward her until it's within the leash range. If Jaina is dead, she can still order the Water Elemental about, and it is no longer bound by the leash range.
Chilled bonus damage: 31 (Per attack and per enemy)
Annoyingly, even though Jaina can order the Water Elemental about while dead, any disable that prevents input of Ability orders will block Jaina from giving orders to the Water Elemental.
target time is 32 seconds of duration
code implies range 12 is maximum retarget distance
scans for enemies in radius 12
1 Slot

Improved Ice Block
Cooldown: 40 seconds (0.5 seconds before reactivation)
Windup: Instant
Must be unlocked by inflicting 12,000 Spell damage to Chilled Heroes.
Activating puts Jaina into Stasis for up to 2.5 seconds. (The effect can be ended early by reactivating the Ability) When Jaina exits the Ice Block, all enemies within radius 5 are Chilled.
If Jaina has done 30,000 Spell damage to Chilled foes, Jaina becomes able to move and use Abilities while this effect is active.
A neat bit of convenience worth noting: all number slot Abilities in Heroes of the Storm can actually be moved to whichever slot you prefer! Simply click and drag and there you go. This is more pertinent for keeping your hotkeys consistent with Talent-derived Abilities than with innate extra Abilities like Improved Ice Block here, as it starts every match in slot 1 so there's no variability unless you choose to move it yourself, but it's a nice quality of life feature I wish the game did more to draw the player's attention to.
should point out that the damage total is not Level-scaled and so as a match drags on it gets easier to complete, more than doubling potential progress speed by Level 20 -before taking into account Talents! (actually less sure prior is true: seems to measure off base damage?)
Level 1 Talents

Winter's Reach
Frostbolt's maximum range is raised from 10.5 to 13.5, and its travel speed travel speed is increased from 15 to 19.5.
The code additionally indicates that Frostbolt's projectile length is increased from 1.6 to 2, but it's difficult to be sure from testing whether this is actually so or not.
i think it isn't so... but unsure

Lingering Chill
The Chilled status has its base duration raised from 4 seconds to 6 seconds.
It's worth pointing out that this makes it possible to sustain the Chilled status on a target indefinitely by just hitting it with Frostbolt every time it comes off cooldown. There are other ways of achieving sustained Chilled status available at later levels, mind, but this is your only option earlier than Level 7.

Fingers of Frost
Initiates a Quest, which advances 1 step per Regeneration Globe collected by Jaina, adding 0.1 Mana regeneration per second. At 20 steps of progress (ie 2 Mana per second added) the Quest is considered completed, raising the Frostbite damage bonus from 50% of base damage to 60% of base damage.
The two effects of Fingers of Frost are both fairly low-impact, and the Quest will take quite a while to complete if you're not aggressively rotating through lanes/camping/otherwise pursuing Regeneration Globes. On the other hand, it's much more generally relevant of a Talent than Winter's Reach (It benefits all your Basic Abilities plus your Heroic, not just Frostbolt), is the only Talent at this tier that directly improves Jaina's damage output, and the instant you grab even one Regeneration Globe it's already helping to ablate one of Jaina's key flaws; that she's incredibly Mana-hungry and by default is regularly forced to Hearth to recover her Mana.
code says 0.1015 Mana regen, not 0.1: think it's wrong though? would only be 0.03 added Mana per second though
Level 4 Talents

Frost Shards
Frost Bolt now penetrates through the first two enemies it hits, only terminating when it hits a third enemy.

Arcane Intellect
If Jaina has more than 75% of her maximum Mana, she gains +10 Spell Power.
When Jaina lands a Basic Attack on a Chilled target, she restores 5 Mana.
When Jaina hits at least 1 Chilled target with any of her Basic Abilities, she restores 20 Mana.
Note that Arcane Intellect's Mana gain is not per-target. Catching 5 Chilled targets with Cone of Cold still only gets you 20 Mana. Blizzard can trigger the refund once per wave, though, so it can refund up to 60 Mana per use.
Nonetheless, if you're not whiffing shots a lot or otherwise failing to hit Chilled targets, Arcane Intellect pretty much solves Jaina's Mana problems for the rest of the match; a Frostbolt effectively only costs a measly 10 Mana, Blizzard can be reduced to effectively 30 Mana, Cone of Cold effectively only costs 20 Mana, and if you're slipping in Basic Attacks to boot you're adding up to 5 Mana generated a second on top of innate Mana generation.
Put a different way, you go from Frostbolt draining 7.5 Mana per second, Blizzard draining 6/s, and Cone of Cold draining 4/s for a total of 17.5 Mana drained per second of intense combat (Ablated some by the baseline 3 Mana generated per second, but the final result is still that intense combat will drain Jaina dry in under 40 seconds) to Frostbolt draining 2.5/s while Blizzard and Cone of Cold each drain 2/s for a total of 6.5/s; with just basic Mana generation that means intense combat can be draining less than 3.5/s (Which will take more than two minutes to drain Jaina dry), and if you're reliably slipping in Basic Attacks on Chilled targets on top of all that your Mana balance outright becomes positive!
Now, this model can't fully align with reality (You're never going to literally have every Ability use hit a Chilled target, nor are you liable to actually be Basic Attacking a Chilled target every single time your Basic Attack is ready), but it's still a pretty good illustration of how dramatic an impact Arcane Intellect has on Jaina's Mana economy.
Notably, any Chilled target counts; there's a lot of Talent bonuses that only kick in when hitting Heroes in particular, but this isn't one of them. This means even if the enemy team is managing to outmaneuver you such that you whiff shots on Heroes a lot, you can still be reliably benefiting from it when fighting in lane, it means Arcane Intellect makes mercenary camps much cheaper for Jaina to take,
This also all means the Spell Power bonus can actually be held onto for a surprisingly long time.
Do note that Jaina's Heroic Abilities don't trigger the Mana refund.
possibly increases Water Elemental damage by 15% of base? either that or 10%

Frost Armor
Enemies that target Jaina with a Basic Attack become Chilled after their projectile arrives. Additionally, Jaina gains a charge of Physical Block, giving her +75 Physical Armor against the next Heroic Basic Attack targeted at her. This charge refreshes 9.9375 seconds after it's used up.
even works on Structures and stuff!
Level 7 Talents

Ice Lance
If Frostbolt hits at least one Chilled target, its current cooldown is reduced by 2 seconds and Jaina is refunded 10 Mana.
tocheck: multitrigger with Frost Shards?

Ice Floes
Cone of Cold's width is increased from 45 degrees to 90 degrees. Additionally, for each Heroic enemy it hits, its current cooldown is reduced by 2 seconds (4 seconds if the Heroic enemy was Chilled at the time), to a maximum of 8 seconds of cooldown reduction. (ie its cooldown can be reduced to 2 seconds by hitting 4 Heroic enemies, or by hitting 2 Chilled Heroic enemies, or 1 Chilled Heroic enemy and 2 Heroic enemies who are not Chilled)

Icefury Wand
Jaina's Basic Attacks gain bonus damage against Chilled targets, and hitting a Chilled target reduces Blizzard's cooldown. Against non-Heroic enemies, the damage bonus is 50% of Jaina's base damage (ie +30 damage) and the cooldown reduction is 1.25 seconds. Against Heroic enemies, the damage bonus is 100% of Jaina's base damage (ie +60 damage) and the cooldown reduction is 2.5 seconds. Basic Attacks that Miss don't trigger Icefury Wand.
Level 10 Talents

Ring of Frost
or

Summon Water Elemental
Level 13 Talents

Storm Front
Blizzard's maximum range is raised from 7 to 12.25, and its radius is raised from 2.5 to 3.25.

Ice Barrier
25% of Spell damage dealt to Chilled targets is granted to Jaina as Shield HP. The Shield HP has a maximum duration of 4 seconds, but this duration is refreshed every time more Shield HP is generated by Ice Barrier. There is no limit to how much Shield HP Jaina can stockpile.

Icy Veins
Extra activatable ability
Cooldown: 60 seconds
Windup: Instant
When activated, Jaina's Basic Abilities have their Mana cost reduced by 50% and their current cooldowns are reduced by 0.25 seconds every 0.125 seconds (ie 3 seconds of cooldown occur per second that passes) for the next 5 seconds.
Level 16 Talents

Snowstorm
Blizzard's second wave adds 50% of base damage. (ie +71 damage) Blizzard's third wave adds 100% of base damage. (ie +142 damage)
Reminder that Chilled's innate damage bonus is a thing and modifiers are additive; against a standing target you're switching from 100%/150%/150% to 100%/200%/250%.
Also, a janky bit is that the damage bonus will be reset if you cast a new Blizzard before the first is done. ie if you cast a second blizzard just after the second wave of the first Blizzard hits, the third wave of the first Blizzard won't get Snowstorm's damage bonus. Icefury Wand plus Icy Veins can produce this situation all on its own, not even getting into other Heroes helping reduce Jaina's cooldowns.

Northern Exposure
Non-Structure enemies hit by Cone of Cold suffer -25 Universal Armor for up to 2 seconds.

Numbing Blast
Enemies that are already Chilled when Cone of Cold hits them are Rooted for 0.75 seconds.
Level 20 Talents

Cold Snap
0.5 seconds after Ring of Frost's ring times out, a 2.5 radius area inside the ring hits all enemies inside it for 310 damage and Roots them for 3 seconds. Every Heroic enemy hit by either part additionally reduces Ring of Frost's current cooldown by 15 seconds.
doesn't need to Root

Wintermute
Summon Water Elemental's maximum cast range is increased from 8 to 11.2. Additionally, the Water Elemental will cast Jaina's Basic Abilities for free after she casts them, doing 40% of her final damage. In the case of Frostbolt and Cone of Cold, they will be cast from the Water Elemental's location toward the point Jaina's player clicked right after Jaina finishes her cast animation, while in Blizzard's case it will be cast to Jaina's Blizzard location after her third wave lands, even if the Water Elemental is far enough away that this should be beyond the cast range.
The Water Elemental benefits from almost all of Jaina's Talents that affect Basic Abilities, only missing out on Arcane Intellect and Snowstorm.
Do note that the damage penalty is achieved through having different base damage on the Water Elemental's versions of these moves and so the Water Elemental will do half Jaina's final damage even after damage boosts get involved.
copying Blizzard has a recovery of 0.15 seconds. Base damage of 71
copying Cone of Cold has a windup of 0.125 seconds. Base damage of 110
copying Frostbolt has a windup of 0.05 seconds. Base damage of 92

Ice Blink
Extra activatable ability
Cooldown: 60 seconds
Windup: Instant
Teleports Jaina to a chosen location within range 4. All enemies within radius 3 of her arrival point are Chilled.
teleports don't work while rooted, but ignore movement
'frigid transmission' in the code, which is a much cooler name

Deep Chill
A Chilled target that has Chilled applied again has the Slow raised from -25% to -40%.
todo: what if the Slow was purged but not the Chilled status?
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Next time, we cover Tyrande.
See you in the Nexus.