Ladrian

Waiting for the attacking signal, Ladrian pulls his crossbow and aims at the same giant as Vigan.

Attack: 27 Damage: 13

 Ladrian uses his movement and, with his bonus action, he uses cunning action to dash to U21

Andor

As the others ready themselves for attack Andor's eye crackle with electricity, the winds whipping around him the sorceror shapes the winds themselves, taking the swirls and eddies and pushing the buffeting winds straight at the trio of stone giants ahead of him.  Waiting for the ranged assault of his companions to be over for a moment Andor jogs forward hugging the rise and draws power to cast a new spell, still unsure of it's effectiveness but hoping for the best.  As he casts the spell the two closest giants are engulfed in a mass of strange symbols, random and enthralling designed to slow their minds and stop their ability to fight on. Over the winds and the commotion of battle Andor screams out to his companions "If they stop moving leave them alone and hit the other ones! It'll give us a bit more time".

casts Hypnotic Pattern DC15 Wisdom to resist

The stone giant (1) is stung yet again as Ladrian's shot catches him squarely in the chest. Immediately thereafter, Andor creates a twisting pattern of color flashes around two of the giants...

...and both of them become overwhelmed by the effects of the spell. They stand where they are, in a stupor and incapacitated.

The remaining stone giant (2) moves in a clockwise direction around the outside of the ruins walls to a point where it can see Harshnag clearly. It then hurls a mass of stone at the frost giant.

• Ranged rock attack (w/ disadvantage due to high winds): 22 | Bludgeoning damage: 19

The stone giant's rock sails harmlessly past Harshnag, who turns and, with greataxe raised, charges at his assailant.

• Greataxe attack: 29 | Slashing damage: 35

The stone giant staggers backward a few feet after absorbing the massive hit from the frost giant.

(Harshnag's attack was the first of round 2; all players may act)

Updated map: 

Andor

Moving further to the east (b19) Andor gets a better sight of the giant fighting against Harshnag, and casts his ray of frost at the foe. "It worked, it actually worked - nobody touch them until we've finished with the other idiot" he calls to the rest of the group as he throws his spell.

Casts Ray of Frost attack 13 for 6 cold damage

Rixton:

Seeing my target become entranced by Andor's magic, I shift targets. I move a little closer (e16) to the active giant but keep some distance, choosing to fire again on Harshnag's right side. Before I loose my arrow, I activate my clockwork amulet, giving me a brief window into the patterns and rhythm of the battle.

Short bow (+1 with +1 arrow and sneak attack damage) attack: 18, Damage: 13

Ladrian

Catching the warning from Andor he uses his movement with Cunning Action to b15 and shoots his crossbow with sneak damage towards the giant near Harshnag

Attack: 12 Damage: 19

With two of the stone giants rendered harmless for the next minute, Andor, Rixton, and Ladrian focus their attacks on the giant locked in combat with Harshnag. Rixton's attack is the only one, however, to find its target. His arrow pierces the stone giant's left shoulder, but the massive creature takes little notice of the injury as it prepares to retaliate with its greatclub. 

(Actions for Carrow and Vigan are next; the stone giant will then follow)

Vigan

Seeing two of the giants stop stone (pun intended) dead, and the third take a savage blow from Harshnag, the goliath chooses not to throw any more javelins, for fear of hitting the wrong giant.  Drawing his glaive, and not wanting their new ally to take all the glory for himself, he sprints towards the battle.

Carrow 

Remaining still he watches his companions surge forward. Remembering Andors words he sees two Giants stop seemingly entranced, focusing his own eyes now away from the beguiling shapes of the spell, the ranger draws his bow and fires. +1 Arrow

Attack1: 14

Hail of Thorns:  10.  Dex 12

Attack2: 22

Hail of Thorns:  9.  Dex 12

Carrow 

OOC: To avoid the dreaded manipulated dice roll I've posted damage here.

Attack1  Damage: 12

Attack2  Damage: 12

Carrow sets his feet and draws his bow, releasing two arrows. The first strikes the stone giant, who is then unable to avoid the rain of thorns that ensues. The ranger's second arrow sails over the giant's head and disappears into the rocks and snow behind it.

The stone giant, enraged at being struck in rapid succession by a bolt and two arrows, levels two herculean swings of its greatclub at Harshnag...

• Greatclub attack 1: 26 | Bludgeoning damage: 22
• Greatclub attack 2: 11 | Bludgeoning damage: 19

Harshnag easily blocks the first swing with his greataxe, but the stone giant's quick reflexes allows him to land his second blow. The sound of the club smashing into Harshnag's plate armor echoes across the mountainside. Harshnag's response is to emit a short laugh before responding with two ferocious swings of his greataxe...

• Greataxe attack 1: 26 | Slashing damage: 33
• Greataxe attack 2: 17 | Slashing damage: 18

The first blow from Harshnag's axe drops the stone giant to one knee; the second blow knocks the stone giant to the ground, where he lies broken and lifeless. Harshnag then turns to look upon the remaining two giants, and with a puzzled look on his face he asks, "What's become of these two?"

(All players may take their actions for round 3)

Vigan

"Andor has a few tricks up his sleeve, but I've not seen that one before."

Vigan approaches one of the giants (#1) slowly, waiting for his luck to turn and its greatclub to suddenly head in his direction.  Confident that it won't move, he hacks at it several times in quick succession while he has the chance.

Attack 1: 16

Damage 1: 10

Attack 2: 27

Damage 2: 8

Bonus Polearm Attack: 14

Bonus Polearm Damage: 8

Action Surge:

Attack 3: 16

Damage 3: 10

Attack 4: 28

Damage 4: 12

Rixton:

I turn and run up behind and next to Vigan (to a13). As I run, I swap my bow for my spear. Skidding to a stop, I plant my feet and lunge at the giant (#1), slashing it with the spear in both hands (using versatile property). I follow this with a roundhouse kick to his knee and, tapping into my stores of ki, turn on my heel and back kick at his other knee.

Spear (+1) Attack: 20 Damage: 16

Kick Attack 1: 8 Damage: 5

Kick Attack 2: 25 Damage: 7

Mercilessly, Vigan and Rixton turn their weapons upon the charmed stone giant standing within the ruins. After Vigan's multiple slashes with the glaive startle the giant out of its magically-induced haze, Rixton delivers the final fatal blows. The giant falls face forward like a felled tree and crashes violently into the granite floor. 

The third and final stone giant now stands alone, staring into nothingness with his greatclub hanging loosely in one hand.

(Round 3 actions for Andor, Ladrian, and Carrow are next; the stone giant will follow)

Updated map:

Andor 

"Everyone, let's do this together,  no sense in giving him a chance to fight back." Andor prepares his new wand for use, after closing the distance slightly. 

Carrow 

Listening to the caster Carrow approaches to within 60ft of the giant and casts hunter mark. Readying his bow he waits for the nod. "Ready" 

(As soon as Ladrian completes his round 3 action--which I assume will not be an attack upon the incapacitated giant--all players may then immediately take their actions for round 4. Harshnag will attack in round 4 only if the last stone giant survives the barrage from the five players)

Andor

Let's see what this thing can do!" He unleashes a barrage of magical missles at the dazed stone giant, the magic steers them unerringly to their target. Eight glowing blue darts slam into the giant causing cracks in his hardened skin.

Casts Magic Missile at 6th level (1 charge remaining on wand) for 27 force damage

OOC Sorry just reread the above post, I've jumped the gun, shouldn't make a difference but apologies anyway!

(Not a problem, Ladrian's next action can be his 4th round attack)

Ladrian

Seeing the downed giant he moves closer to his friends at Z13 with his crossbow aimed and ready at the remaining giant.

"Ready when you are" Ladrian whispers to the others.

Trigger for the ready action is when everyone starts to shoot at the giant.

Attack: 9 Damage: 9

If there's anyone near the giant at the time of the attack I'll roll here sneak attack damage, if not please disregard it: 9