The Phandalin Chronicles

Dex Save: 12

Rhogar's Dexterity Saving Throw(DC 12): 21.
Adv. Roll: 20. (if considered a spell or magical effect)

Ghorar's Dex Save(DC 12): 7.(If she counts despite being on Rhogar's shoulder)
Adv. Roll: 4. (if considered a spell or magical effect)

"What Dark Sorcerery is this!?" Rhogar exclaims while waving his axe at the routes and attempting to retreat from them.

Chip dex save! 14

"I didn't do this! This was not my fault!" Chip would shout as he feebly attempts to swing his lute at the roots as they batter and bruise the dragonborn. 

Kazri Dex Save: 2

(OCC: Kazri was very nervous, so she totally didn’t see that coming. :-)

(OCC: Question: Can I the shield’s AC for the roll in this case. Curious if that applies here.

Shield Master: If you aren't incapacitated, you can add your shield's AC bonus to any DEX saving throw you make against effects that target only you, and if an effect allows half damage on success, you can use your reaction to take no damage.)

Chill watches from the trees as the others are caught in the entangling roots that have erupted from the ground.

"Get out of there!" He yells waving to the others. 

Dex save 7

"By Moradin's Flaming Beard!" shouts Krom as the entangling roots erupt from the ground. "Chill! Shoot the tree!, Everyone let's destroy this dark creation."

Krom tries to avoid the roots and prepares to counterattack.

Chip and Kazri (I don't think the shield master things applies but it wasn't going to improve your 2 enough anyways) are injured as they become restrained.  Ghorar tries to fly off of Rhogar's shoulder as the roots erupt around him but gets knocked to the ground and is also restrained.

• A restrained creature's speed becomes 0, and it can't benefit from any bonus to its speed.
• Attack rolls against the creature have advantage, and the creature's attack rolls have disadvantage.
• The creature has disadvantage on Dexterity saving throws.

We'll handle this in rounds, state your actions just like combat including attacks.  The roots don't have a turn and don't take actions.  Post in any order you wish.

Seeing Ghorar survive, if only by the skin of her teeth, Rhogar snaps his fingers, causing her to rapidly transform into a fast dispersing blue mist. Once she is fully gone, the thin shimmer of magic about the Dragonborn disappears as well. "Seconded Master Krom! Chill! Worry not of us, and do as he's requested! Aim for the center mass of the figures!" He called out, as he himself circled around to the opposite side of the tree from the others.

The others could work on free themselves, or so he silently hoped for...

Action: Dismiss Ghorar to her Pocket Plane.

Kazri tries to free herself from the roots. (Strength Save: 14)

Chill lifts his cross now up and fires at the tree.

Attack: 13 Damage: 6

"Time to burn this tree down!", Krom moves towards the cursed tree and chanting an hymn of evocation (Searing Smite) swings his warhammer, now flaring with a white-hot intensity, at the tree.

Bonus Action : Searing Smite Fire Damage 3   DC Con 14 for each following rounds to avoid taking another 1d6 Fire Damage

Blessed Warhammer Attack : Attack: 26 Damage: 14

Rekuberk will crack his knuckles and move to slam into the tree with the mail that Krom had made for him, not sure his sword would have been much help.

Maul: Attack: 21 Damage: 15

Chip would snarl as he fights against the branches before releasing a wave of flame from his open mouth towards the tree, turning his head to avoid hitting any companions!

dex 12 or take 4 fire damage!

Kazri tries to free herself from the roots that have entangled and restrained her but she is unsuccessful and takes another 3 bludgeoning damage.

Chip doesn't even try to free himself as he sends a gout of fire at the tree.  Flames start to lick up the side of the tree as the roots deliver another 6 bludgeoning damage to him.

Ghorar evaporates into a blue mist as the rest of the party attacks the tree.

Krom's hammer blow adds flames to the already burning tree as Rekuburk slams his maul into the tree and it shudders from the hit.

Chili's bolt flies past the tree and misses.

Chip and Kazri still restrained.

Rhogar raised his axe at last, finally ready to join in on chopping down the tree. However, in realizing both Dragonborn and Knight had to free themselves, a grumbling Bronze makes his way back over, shouting out a word of power as he swept the blade across one bindings with a burning blade. More leap to Kazri next, hopefully weakening her binds, if nothing else. "Come now, Brother. This is NO time to be resting on your laurels." He half jokingly states.

Action: Cast (Cantrip)Bursting Blade - Attack: 15 Damage: 7 slashing and fire damage to Chips vines, and 6 fire to Kazri's bindings(if possible).

(If above is considered a 'miss', using Favored By the Gods; adding 7 to the attack roll)

"Moradin!" shouts Krom as he swings one more time his hammer against the cursed tree. 

Blessed Warhammer : Attack: 12 Damage: 14

I didn't clarify, for Chip and Kazri, its a DC 15 Strength (Athletics) check to break free from the roots.

Rhogar slashes the roots entangling Chip and seeing that his blow will glance off calls on the favor of the gods and his ax cuts into the roots and frees Chip.  While the flames leap from the blade to the roots holding Kazri they do not release the roots from her.

Kazri tries to free herself from the roots but is again unsuccessful (I took your first roll and added your athletics bonus but 12 still wasn't enough)

Krom continues to hammer on the tree. 

(Thanks for the clarification. I did do a strength check b4, but wasn’t sure if that was the right check.)

(Also, I would like to point out that Kazri is NOT having a good time now. :-)

Chill continues to watch from the edge of the clearing.  He sends another bolt at the burning tree.

Attack: 16 Damage: 18