Regular piercing damage plus the cold damge.

Alright, Dex save 2 for the shadow thanks to Temphalic:

6

Quote from Ben_Evolent >>

Elf Shadow - DEX saving throw: 9
Hewelathan - DEX saving throw: 18

(OOC: OK. It looks like Jodie passed her DEX saving throw and maintained her concentration.  Therefore, Tamphalic used his Chronal Shift to help the Elf Shadow since everyone else passed their saving throws.  We also need a CON saving throw from Hewelathan for concentration on Pass Without Trace.  Since the Elf Shadow starts at 16 HP, it will be the target of Zolgu's knife unless the fireball destroys it.  Otherwise, Tamphalic would be the target since Hewelathan is relatively uninjured and Jodie's still invisible.)   

• Elf Shadow - rerolling DEX saving throw (chronal shift): 8
• Hewelathan takes 15 (fire) damage, reduced by his 12 THP.  DC 10 CON saving throw 10

I think that Hewelathan would was probably the only one whom Zolgu could see that was in range for his dagger throw (range 20/60, I forgot about that initially and he would target someone he had a good chance of hitting). So, that's who he threw it at. Sorry, Hew.

Quote from Mister_Whisker >>

I think that Hewelathan would was probably the only one whom Zolgu could see that was in range for his dagger throw (range 20/60, I forgot about that initially and he would target someone he had a good chance of hitting). So, that's who he threw it at. Sorry, Hew.

(OOC: Better Hewelathan than Tamphalic.  So, we've resolved the results of Zolgu's turn.)

Hewelathan takes 8 dmg from the knife, so it requires another saving throw for concentration. 

Hewelathan - CON saving throw 22 

Round 3: Gorash

Gorash was planning to attack one of the cultists until he sees the little kobold cast his own fireball.  Despite the kobold's cover, Gorash tries to target him with a spell.  He also attempts to move into an area where he'll have some cover.

Action: Cast Freezing Ray (120 ft) at Zolgu: 16, Damage: Unable to parse dice roll. (cold)
Movement: Move 30 ft. toward the cluttered area toward the east, trying to find half-cover or 3/4-cover.

(OOC: See OOC thread.  I misunderstood Gorash's stat block.  If allowed, I think that @Faux_Beau is right, and Gorash would first try to dispel what looks like a fire shield on Zolgu.  Since it's probably a > 3rd level spell:

Gorash - INT check 9

Quote from Ben_Evolent >>

Round 3: Gorash

Action: Cast Freezing Ray (120 ft) at Zolgu: 7, Damage: Unable to parse dice roll. (cold)

---

Gorash - INT check 3

(OOC: Ugh!  Either way, Gorash is ineffective this round!  DM's ruling is to go with the initially action: attack with Freezing Ray.)

Anyway, looks like Korba and Hew are up, followed by Ruby.

Round 3: Korba

Korba is worried that Zolgu may become invisible again, and he's just close enough to reach Zolgu and maybe his cultist ally with a spell.  Hoping that he doesn't catch Jodie in the AoE, he casts Faerie Fire.

Action: Cast spell (LVL 1 slot) Faerie Fire, 20-foot square, covering both cultist #2 and Zolgu, as shown on the map.
  Outlines all objects and creatures in the area in green light.  Creatures must pass a DEX 15 saving throw to avoid the effect.
  Attacks against affected creatures or objects have advantage, and affected creatures or objects lose any benefits from being invisible.
Movement: Korba moves farther west for now, trying to stay out of the cultists' spells and avoiding getting too close to the other Accursed.  He'd like to get closer and use his sword, but he knows that he can still reach Zolgu with eldritch blast, and he feels like it's more important to ensure that the group can still see Zolgu to hit him. 

(OOC: I updated Korba's position and marked the spell's AoE in green on the map.)

Cultist 2 Dex save: 18

Zolgu Dex save: 12

Round 3: Hewelathan

Hewelathan-bear luckily dodged behind a rock, avoiding the worst of the fireball.  But seeing the magical power of these foes and the warding spells in place, Hewelathan feels like he needs more ranged attack options and the flexibility to cast more spells.  He'd really like to go after Zolgu, but he wants to try to clear the way for Jodie to get to Cynurrarth first.  The dragon may be injured, but it's still a dragon, and it could help them deal with the cultists.  

Hewelathan drops out of Wild Shape and hurls a javelin at Death Cultist #2.  He risks getting closer to Zolgu, hoping to provide Jodie with the benefit of pass without trace for a little longer.

Bonus Action: Dismiss Wild Shape.
Action: Attack Death Cultist 2, javelin (30/120): 28 Damage: 13
Movement: East into the mess of tipped-over shelves, ending with 1/2 cover from Zolgu if he can find it.

Quote from Ben_Evolent >>

Round 3: Hewelathan

Action: Attack Death Cultist 2, javelin (30/120): 12 Damage: 15

(OOC: Sigh.  Someone with a +11 to hit shouldn't have to spend luck points to hit, but here we are.  Re-rolling the attack.) 

13

...

Somehow, even with the luck point, Hewelathan misses his target.

At the end of Hew's turn, Zolgu the Great Wyrm uses two legendary actions to hurl another dagger at the Druid...

Dagger attack:

Attack: 11; Damage: 6 piercing + 1 cold

The four mirrored Rubies look furious at Zolgu's betrayal.  She stands over the other dead cultists as she takes aim at the glowing Zolgu as she shout in Draconic,

"You have betrayed dragonkind.   You unworthy to lead."

Arcane burst 1: 21 Damage: 10 force

Arcane burst 2: 10 Damage: 3 force

As the magical dust settles an outlines Zolgu, Jodie reminds herself free the dragon first and foremost.  She moves towards Hewelathan to be aided by his stealthy aura as she passes between him and Zolgu amongst the fallen bookshelves.  

Jodie sings a verse (bardic inspiration) for Hewelathan

You can make it if you try

Jodie traverses the terrain to get as close to Cynurrarth as possible.

In a quiet voice only a nearby dragon could hear, the invisible bard greets the chained and wounded Cynurrarth

"Great Cynurrath, I'll dissolve your chains with magic dust.  Just in time to avenge your brethren and kobold children of another villain of the Underdark. Oh what a song it'll make what's done today...then I hope you'll see things square."

Persuasion: 16

(OOC: Updated map at the start of Hildegard's turn.  @Faux_Beau updated Jodie and Ruby's positions.  I added "condition markers" for Nickeline's Sanctuary and for the bardic inspiration that Nickeline and Hewelathan have.) 

Even with half-cover, Ruby would have hit the white kobold with both of the beams. At the last moment, the white kobold hisses a spell, surrounding himself with a magical barrier.

(OOC: Both of Ruby's arcane blasts hit the Shield instead of Zolgu?)

As Jodie approaches, Cynurrarth whispers back to her.

"Hurry and free me, Bard. I shall consider your debt paid in full."

Quote from Ben_Evolent >>

(OOC: Both of Ruby's arcane blasts hit the Shield instead of Zolgu?)

Yep... it's amazing how much of a difference half-cover makes. And maybe a magic item as well.

But she made him burn a spell, so there's that.