Hit. Storm is up.

Casey was more then 20 feet away but this will apply to storm and Aino.

Fear Aura. Any creature hostile to the pit fiend that starts its turn within 20 feet of the pit fiend must make a DC 21 Wisdom saving throw, unless the pit fiend is incapacitated. On a failed save, the creature is frightened until the start of its next turn. If a creature's saving throw is successful, the creature is immune to the pit fiend's Fear Aura for the next 24 hours.

OOC: So with Aura of Courage Storm is immune to being frightened and so are all allies within 10 feet of Storm, which I believe Aino is next to him. Also this includes the griffon he is on.

Storm will look up at the demon, a glint in his eye, "I could smell your foul stench creature! You will not survive this day!"

Bonus Action: Mark demon as new target for Hunters Mark, also just realized Ive been forgetting to make the concentrations checks for Hunters Mark so I just rolled 8 of them to be safe with the lowest one coming in at 16 which means all good since highest damage would have put DC at 13

Attack 1: 34 Damage: 23 slashing + 13 radiant + 15 necrotic

Attack 2: 31 Damage: 22 slashing + 9 radiant + 10 necrotic

Haste Attack: 36 Damage: 17 slashing + 14 radiant + 19 necrotic

Total damage: 62 slashing + 36 radiant + 44 necrotic = 142 damage

Griffo Action: Dodge

Hit. The voidling is looking less corporeal.

The Voidling is up.

Since storm has done the most damage he will be targeted.

The Voidling looks into your eye and you see deep into the vastness of the void. You start to feel your mind break. (Legendary action)

Make a DC 20 Wisdom save or be Incapacitated. You can reattempt the save at the end of your of your turns.

If you pass he will attack you. If you fail he will attack Aino

Attack: 16 miss

Attack 2: 26 hit 13 damage

Attack 3: 18 miss

Attack 4: Nat 20 hit 14 magic bludgeoning 24 fire damage (reduce as required)

Storm has 27 AC and Aino has 29 base AC, so I think attacks 1, 2 and 3 all miss us either way (Attack 2 does NOT hit even though it's a 26).

Whoever attack 4 (CRIT) is on, Thumbtack from 50' up uses her Ring of Spell Storing to cast another Silvery Barbs spell as a reaction,  forcing a re-roll of the attack and giving Aino advantage on her next d20 roll.  First of two Rings clutched by Thumbtack now empty of spells.

Don't forget extra 1d4 from the Potion of Heroism on the WIS Save for Storm.

I'll be out the entire day.  Will post again late (Pacific time zone).

OOC: 28 on the wisdom save and yes Storms AC is 27 so the 26 would miss as well. I will wait for the re-roll for the last attack.

Reroll 33 to hit

OOC: 26 Concentration on the damage from the re-rolled hit

Aino is within 10' of Storm - cannot be frightened due to Paladins' 10th level Aura of Courage.  So I won't roll the DC21 WIS Save for the Fear Aura.

Thumbtack stays up 50' above, taking the dodge action.

Aino attacks three times due to the Potion of Speed, the first one at advantage due to Silvery Barbs and 3d20s due to Elven Accuracy.  Using Booming Blade on the first attack.  First two with her Rapier, +3, third using her Staff of Power to hit the Voidling with a Ray of Enfeeblement making all his attacks do half damage until Aino's next turn.

Attack 1: (Rapier, +3 with Booming Blade, best of 3d20s)
To Hit:  35 + 1 from Potion of Heroism = 36
Rapier, +3:  21 magical piercing damage
Booming Blade immediate effect:  11 thunder damage
Booming Blade secondary effect if Voidling moves:  15 thunder damage

Attack 2:  (Rapier, +3, straight roll)
To Hit:  25 + 4 from Potion of Heroism = 29
Rapier, +3:  24 magical piercing damage

Damage from first two attacks:  56 (45 magical piercing and 11 thunder)
Plus 15 more thunder damage if the Voidling moves.

Attack 3:  (Staff of Power, casting Ray of Enfeeblement, straight roll)
(To avoid disadvantage on the ranged spell attack, she casts Misty Step as a bonus action to move 30' away first).
To Hit:  31 + 4 from Potion of Heroism = 35

Result:  Voidling does half damage on all his attacks until Aino's next turn, no saving throw.

Hit Casey is up.

The voidling is starting to look transparent 

(Busy day sorry! )

Casey’s spiritual weapon attacks once, she attacks with 3 eldritch blasts, and she does a flyby to whack with her staff from the back of the griffon, which helps her and then uses its haste move to disengage..

Spiritual weapon:  35 +3for 13 damage 

eldritch blasts 35 +3 to hit for 9

30 +1 to hit for 13

natural 20+4 to hit for 17

Staff:

33 +2 to hit for 11 

totals:

50 damage (39 force, 11 magical bludgeoning)  and he’s knocked back 3x 

Two things happen. First hit and the voidling is knocked back causing the thunder damage. Causing the Voidling to go completely transparent.

(He went down quickly I grossly underestimated how well you would do in the first part of the fight thought you be a bit more spent)

Second. A large rip in space time opens up. That starts to suck everyone within 200 feet in. Make a DC Str 20 save, let's do dex if your flying, or be pulled into the Void.

Lol 2/3 of the spectators are pulled in.

Casey is sucked in! 

Oh no, Casey!

Aino, on the other hand, gets overkill.

DEX Save:  Nat. 20 + 8 + 5 from Storm's Aura + 2 from Potion of Heroism = 35

(Didn't even have to use Bardic Inspiration or Lucky feat).

I assume we are still in Initiative and Aino has to wait until her turn to cast something like Forcecage or Wall of Force around it.

Edited to add:  Thumbtack, on a custom 1d20+1 DEX Save gets a 2 (Nat. 1) and is the first pour soul sucked in ahead of everyone else!  Aino screams despondently... mostly about Casey but a little bit about her owl Familiar.

If it is a spell, Aino would try to Counterspell it as a reaction, but I don't think this is a spell effect, right?

Yep also with your Int you get the since only way to close the rift is via magical damage.

Casey, spinning on her griffon, her triumphant smile turns to horror as she is pulled into the void.

Through the telepathic bond she calls to the group “Mayhap I’ll be ok, this staff’s got some tricks it can do.  Let’s get this thing closed if we can, feel bad fer the Crowds and don’t wants it destroyin the city or more..   I’ll try to get yer owl and me griffon if I can!”  

Correct Aino's knowledge of the Arcane would let her know this is not a spell.

We are still in initiative once storm makes the save I'll post what everyone is seeing then we will pick back up with storm.

No pressure but where he us will mater.

OOC: Storm 34 total, his griffon 31 total 

Alright. The rift opens up. Thumbtack's tiny body is quickly sucked in. Casey caught off guard celebrating is also sucked in along with her.

Aino and Storm are able to withstand the force pulling at them. Most of the crowd was not and is sucked into the portal. The Portal currently has a effect out to 200 feet. Every round that area will double.

Casey as you are sucked in you are tossed 419 feet into the void. Getting your bearings you see a few things. 1 Thumbtack is halfway between you and the rift, 2 the voidling is here and coming after you. (100ft away from you further away from the rift) 3 there are dozens of voidlings all around, last you see a familiar figure appear before you.

It's death but for the first time you see (s)he is not wearing a hood. Death looks like how ever you picture (s)he to be and every time you blink its face changes to a different one.

Death: You should not be here. This is no good we need to get you out and seal the rift. Head to the opening I'll hold him off for as long as I can.

Confused you turn looking over your should asking who.

You see the elder God Void coming towards you. The size of a planet and perfectly dark. You freeze in terror, then your mind screams run. 

Death whispers in your ear.

Fight it don't give in. Use your winning personality to combat this. Remember your a faking artist use to pressure.

Casey on your turn roll a DC 30 Chrisma save with advantage. On a fail you will suffer the affects of fear.

Storm is up. You are out side the rift seeing random people being sucked in. 

Order: Rift, Voidling, Aino, Casey, Storm

Through Rary's Telepathic Bond Aino would be communicating her realization to Storm:

"... also with your [Aino's] Int you get the since only way to close the rift is via magical damage."

Unfortunately, Rary's Telepathic Bond does not extend to other planes, so Casey is cut off from the telepathy for now, I think.