Qinro fans his nose from the gas, but he is immune to poison.  He looks over the cannon at Aesalor, steps to the side and casts 5th level moonbeam on Aesalor, turning up the heat on him yet again.  

Moonbeam :  DC 18 Constitution save or take 32 points of radiant damage, searing ghostly flames appear on his body extending up in a 40 foot cylinder.  He takes half as much on a made save.  Shapechangers with disadvantage on the save.  

Aranea strikes true with her blade and she significantly damages the remains of Aesalor.

(Dex: 12, Aesalor failed the saving throw but chooses to succeed instead.)

The blast of Jerick's spell strikes Aesalor and does massive damage to him.

Aesalor begins to laugh once more, before clicking his neck.

(Everyone make a DC18 Con save, take 29 necrotic damage on a fail, half on a success.)

(Con: 12, Aesalor failed the saving throw but chooses to succeed instead.)

The beam of light radiates down on Aesalor causing him more damage.

Qinro con save :  14 

Jerick Con save 7 

(Round 3)

Jerick again feels the full brunt of the Aesalor's cursed magic, but necrotic damage affects Jerick less than others. It also triggers a thought in his head. Time to pull out my own necromancy.

Jerick points at Aesalor and casts finger of death at 7th level, causing painful necrotic energy to course through his veins.

Aesalor must make a DC 18 CON save. On a fail, he takes 58 necrotic damage; half that on a success.

Jerick then ducks behind the protector turret to gain some cover.

Glugrug Con Save 25
Con Save for Concentration on Haste 19

The energies from the protector tower help Glugrug shrug off most of the damage from the mage's spell--and he maintains his hasted condition. He opts to follow up fire with ice. "Incoming ice storm!" he calls out to his comrades, hoping they will stay clear once more. He centers the spell slightly behind the enemy mage, then calls down massive chunks of hail and ice.

Casting Ice Storm, Dex Save 18 for half damage
Bludgeoning Damage 10
Cold Damage 16
Terrain in area is difficult until the end of my next turn

Still moving quickly due to the haste spell, he then shoots a fire bolt at the reanimated mage.

Fire Bolt Attack: 22 Damage: 26

The cannons trigger once more, sending fire and healing energy respectively.

Flamethrower, half damage on Dex Save DC 18 15
Protector 10 temp HP

Constitution Save 21

Aranea barely feels Aesalor's magic hit her, although the necrotic energy does make her feel sick. Heeding Glugrug's warning, she sticks close to the protector turret. Now at a distance from Aesalor, she withdraws her crossbow and prepares to launch a bolt into the ugly creature's heart. Again, she focuses her ki to put even more power behind the shot.

Attack 1 22 / Damage 19

Attack 2 11 / Damage 13

Bonus Action: Kensei's Shot (extra d4 damage to ranged attacks for 1 turn)

Qinro keeps the moonbeam focused on Aesalor for another 27 radiant damage, DC con save of 18 to take half.  

He throws a ball of flame at Aesalor.

Produce flame :  Attack: 20 Damage: 15 

Qinro shouts "Time is running out on the hour glass!  Act quick, attack!"

(Sorry, busy weekend that was unexpected we'll extend slightly because of my absence.)

Aranea manages to successfully shoot Aesalor twice with her weapons causing massive damage.

(Con: 23)

Jerick casts a spell at Aesalor but he manages to resist the worst of the spell's effects.

(Con: 6)

Qinfro then attacks Aesalor with his magic spells doing further massive damage.

Then finally, with the attacks from Glugrug Aesalor's remains are destroyed. His body begins to waste away as he turns into dust.

With the last remaining sand falling through to the bottom of the hourglass, the library begins to quake and shake. Books begin falling from the shelves due to the large vibrations shaking the foundations of the library. The roof then cracks as big chunks begin to fall down almost crushing you. Above the roof, you see an empty void of pure nothingness.

Then each of you begins to glow with a golden light, glittering away. You feel a sensation of warmth running through your body as the library continues to fall apart.

Once the library has completely fallen, you find yourself floating in the empty void. All that you can see are the rest of the group also floating in the same sea of nothingness.

Then as you are about to begin to lose hope, you start to see things appear around you in the distance almost as if seeing through a dense fog. At the same time, the rest of the group begins to fade away from sight. Until eventually, you find yourselves standing in the same place as you were before the crazy adventure began.

You are now separated from the rest of the group, but you have survived and you know that you all succeeded in the mission given to you by the gods.