Ben:

Excited, Ben puts his hand in his pocket and holds the mysterious key.  He waits for Titaani though, before trying it in the lock—just because he found a key and the door is locked doesn’t mean this is the right one…but he hopes.

Titaani fails to open the door. But in doing so she's learned that it's actually unlocked. Rather, it's jammed shut with something from the other side. (You can make a Strength check to try to muscle it open if you like.)

Still in the other room, Pud looks over the bent, moldy tools. Picking through it, he could probably salvage an ugly-but-functional set of Tinker's Tools and/or a set of Brewer's Supplies out of it – they'd be utilitarian but valueless. As to the large, bubbling contraption on the table, lit by some sort of open lantern from below, its structural integrity is a little questionable. 

"Ugh, I can't get it open!" Titaani exclaims, stamping her foot angrily. "There's something blocking it from the other side, and I'm not strong enough to push it away."

Ben:

”Titaani, if you can jam the handle unlatched, I can take a run at it and try to push open the door,” offers Ben.

Strength Check (Add 3 is Athletics applies):  18

Ben takes a run at it. Foggy daylight streams into the darkened room as you realize it's an exterior door.

You also realize that the object blocking the door is a huge 7-foot-long, 5-foot-wide wasp nest, now torn in two.

Roll initiative!
Very Angry Wasps: 4
(Anyone who meets or beats it can act immediately!)

Ben hurdles toward the top edge of a rickety, partially broken staircase. Ben: Roll a DC15 Acrobatics check to stop yourself from falling down (or through) the stairs. If you fail, roll a straight d20 to see how bad the consequences are (DC10 to just take 4 bludgeoning damage from the fall but land prone on the lower landing; <10 and you still take the damage but you also go right through the landing and into the lake far below.)

(( 19 initiative ))

Ben:

Before his mind consciously registers how bad of a situation he is in, Ben’s reflexes kick in and he attempts to grab the railing and avoid a very long drop.

Acrobatics:  17

Severity D20:  12

Initiative:  10

(If this is bad and he has a bonus action available, Ben will Misty Step to get back into the main room).

Matilda Initiative- 25

Matilda throws two cleavers hoping to disperse the insects as much as injure any.

Attack: 15 Damage: 4

BA- Attack: 23 Damage: 5

Ben manages to catch himself before he plummets off the top of the exterior staircase. Unfortunately, it puts him in the middle of the swarm of angry wasps.

Matilda throws her cleavers through the center of the swarm, and while she manages to kill a few, she finds it's not the most effective way to eradicate wasps. (Damage Resistance: Slashing)

Horatio may act.

Titaani may roll initiative, and act immediately if she rolls a 6 or higher.

Pud is some 70 feet away at the other end of the cottage and is unaware of what's happening at the moment.

Initiative: 22

Pud rummages through the old equipment. He stops again to admire the odd mechanism in the middle of the room.

"Titaani, this sorta reminds me of an old distillery we had back ho..."

He stops when he realized Titaani had already wandered off. He's startled by the ruckus in the other room where Ben, Horatio and Matilda lingered behind. Now with his leg restored, Pud runs like the wind to check on his friends.

Move: Full movement speed + dash

Action: Dash

Initiative: 22

"Wait! Don't hurt them!" Titaani cries out to the others. Desperately trying to remember what her mother Dianae taught her about the languages of animals, she attempts to speak with the wasps. "Please do not attack my friends. We mean you no harm. We're...um...we're sorry for breaking your home. It was an accident. A mistake. Do you understand?"

(Action: Using forest gnome feature 'speak with small beasts' - persuasion: 13)

Clumsily, Horatio begins to spring into action with uncertainty. How do you fight a swarm? He swats at whatever is nearest him at first, only to realize Titaani is calling for a stop to the fight. 

(( Attack 1: Unarmed Strike - 10 to hit, 10 to damage ))
(( Attack 2: Unarmed Strike - natural 1 to hit (9 modified), 10 damage ))
(( Bonus Action - not taken, Horatio halts his attacks in confusion ))

Pud races into the fray.

"Kill! Kill! Kill!" shout the angry wasps to Titaani, in wasp language. "Revenge! Revenge! Revenge! Protect! Protect! Protect!" 
The wasps seem to understand Titaani's plea, but they aren't quite having it.

Initiative:
Morgort: 2
Elkhorn:  7

Elkhorn raises his sword nervously, but holds his position. "I hate bees..." he announces.

The wasps begin to try to sting Ben:
Sting Attack: 5. Hit: 10 piercing damage

Morgort steps forward. "Wasps, not bees," she utters, annoyed at Elkhorn's comment. Then she utters a very loud croak.
Wasps: DC12 WIS Save (with advantage due to combat negated by Titaani's efforts to calm them) vs. Croak of Charming: 11 

Temporarily charmed by Morgort's croak, the wasps reluctantly pause their attack.
"That won't last long," says Morgort nervously. "We need to do something quick." 

Everyone may act, starting with Ben.

Matilda tried to think of something from home that she's heard would ward off wasps.

Nature- 21

Ben:

Dodging the wasps before they are momentarily calmed, Ben carefully lifts up the half of the nest that is separated from the other and asks with forced calm, “Does anyone have any rope, or maybe a spell that would Mend this nest?”  He gently places the two halves together as best he can tell where they should go and holds it in place.

Pud stumbles into the chaos and tries to figure out what the heck to do. He takes Ben’s suggestion and runs with it.

”I can fix the next!”

Pud casts mending on the wasp nest attempting to repair it.