Matilda moves down to the base of the stairs and sends her magical blade winging towards Warduke's face, then slips behind a pillar out of sight.

It hits Warduke, puncturing his shoulder. He pulls it out and flings it away. He appears in pain.

(Matilda: Make a DC 15 Dexterity check to Hide behind the pillar under the stairs.)

Titaani is up next!

Pud will attack Warduke instead since his original target is no longer with us. 

Matilda Dex- 22

Titaani will throw two eldritch blasts at two different bird creatures!

Blast one: 14 Damage: 12

Blast two: 21 Damage: 10

Matilda successfully vanishes from view.

Titaani releases two beams of crackling energy at the previously-leashed birdlike things, now running loose.
She hits both, but they are tough, scaly things that clearly can take a beating. (Both wounded.)

"He owed me money..." growls Warduke from under his dark helm. His blade bursts into brilliant flames.

Warduke turns his blade on Ben:
Flame Tongue Attack #1: 23. Hit: 6 slashing damage plus 7 fire damage.
Flame Tongue Attack #2: 20. Hit: 9 slashing damage plus 10 fire damage.
Flame Tongue Attack #3: 7. Hit: 13 slashing damage plus 6 fire damage.

Elkhorn races to the bottom of the stairs (Dash.) "Surrender, Warduke!" he cries

Horatio is up next!

Horatio throws his javelin at the remaining enemy (( Action 1: Javelin, 12 to hit, 8 piercing damage )). Then moves to attack him (( Movement to Warduke )), swinging twice with his fists (( Action 2: Unarmed Strike, 27 to hit, 9 bludgeoning damage (includes +1 from d6 from Giant's Might), Bonus Action: Unarmed Strike, 9 to hit, 9 bludgeoning damage )) then trying to kick him in a knee (( Action Surge: Unarmed Strike, 10 to hit, 12 bludgeoning damage )). 

Horatio throws his javelin, but it glances off his substantial half-plate armor.

Moving away from the birdlike creatures, they get in a couple of pecks of opportunity:
#1 Opportunity Bite Attack vs Horatio: 19. Hit: 2 piercing damage, and Horatio must make a DC 11 CON Save...
#2 Opportunity Bite Attack vs Horatio: 14. Hit: 3 piercing damage, and Horatio must make a DC 11 CON Save...

(Assuming he makes any needed saves...)
Horatio circles behind Ben to land one powerful blow on Warduke.

One of the birdlike creatures flaps over to Elkhorn; the other two fly to Ben:
#1 Bite Attack vs Ben: 5. Hit: 3 piercing damage, and Ben must make a DC 11 CON Save...
#2 Bite Attack vs Ben: 19. Hit: 3 piercing damage, and Ben must make a DC 11 CON Save...
#3 Bite Attack vs Elkhorn: 23. Hit: 4 piercing damage, and Elkhorn must make a DC 11 CON Save... (if needed: Elkhorn: 13)

Matilda, Titaani, Ben, and Pud are up next!

Ben:

(Remember +3 saves if within 10 feet of Ben)

Constitution Save:  22

Ben:

Getting hit by one of the aggressive chickens after also taking a wound from the flaming sword, Ben responds by slashing at the Warduke with his sword!

Attack:  8 plus bless 2

Damage:  11

Attack:  21 plus bless 1

Damage:  7

"Leave my friends alone!" Titaani screams at Warduke, her eyes glowing purple. "You-you snake!"

(She will cast polymorph on Warduke, to turn him into a corn snake! He'll need to make a DC 14 wisdom save)

(( Horatio Con saves: 12 and 9 ))

EDIT: If in range of Ben it'd be 15 and 12

Matilda moves up to engage one of the death-chickens with her longer blade looking regretfully at the magical one still stuck in the helmeted man.

Vs Chicken Attack: 16 Damage: 13

BA- Dash back to the pillar. Fancy Footwork avoids AoO.

Pud pops around the corner and launches two more eldritch blasts at Warduke and then warps 15 ft back again to seek cover.

Blast 1: 9 to hit for 1 damage.

Blast 1: 20 to hit for 4 damage.

One of Ben's swings connects. (Horatio and Ben make their saves.)

"I like to hit things with my sword..." growls Warduke his flaming blade high above his head for his next strike, "but..." Then he winces as he tries to stave off corn snake transformation." DC14 WIS Save: 9

Then he turns into a corn snake.

Matilda runs out, unsuccessfully swiping at a bird-like thing before retreating back to safety. (They look like some hideous hybrid of lizard, bird, and bat.)

(Does Pud want to change his turn, now that Warduke is a small snake? The only foes visible are the three formerly-leashed bird things.)

Pud runs into the room and aims his multi-tool wand at Warduke only to see him transform into. He lets out a loud snort of a laugh and then spews some acid at the weird bird things. He blips out of the room and transports back to the staircase.

Attack: Cast acid splash. Two birds make a DC 16 DEX save or take 4 acid damage.

DC16 Dex saves: 12, 11
The bird things titter with annoyance.

Warduke, in snake form, disengages and bolts for the northwest tower door.

Elkhorn hacks at the bird-thing menacing him:
Longsword Attack #1: 9 Hit: 3 slashing damage
Longsword Attack #2: 18 Hit: 1 slashing damage

Horatio is up next!

Horatio bears down on the snake (( Movement 30' )) and steps on it repeatedly. 

(( Action 1: Unarmed Strike, 22 to hit, 11 bludgeoning damage (+3 from Giant's Might) ))
(( Action 2: Unarmed Strike, 21 to hit, 10 bludgeoning damage ))
(( Bonus Action: Unarmed Strike, 24 to hit, 7 bludgeoning damage ))

Horatio chases the small snake across the marble throne room and into the archway of a turret with a tall, stained-glass window set in its walls. The window bears the image of a knight in armor.

He stomps on the snake. Upon the first application of his powerful heel, the snake reverts back to Warduke's armored form. But Horatio doesn't let up, kicking the prone figure again and again.

"Knights of glass..." he cries out horsely, the sound of desperation in his voice, "protect my ass!"

The stained-glass knight leaps from its window frames, raising its glass sword high.

Glasswork Golem initiative: 17