Giles hears the commotion and steps into the room, seeing Burr down on the ground, covered in rats, burrowing and biting into his nether regions.  A shiver goes up his spine as he imagines in his mind that sensation (or even worse, if you were locked inside a bag with them?  I must help him!)  He steps to the side of the door, toward the harp and points toward the rats, a bell sounds around them, casting toll the dead.  As a bonus action, he points at Burr and say “Salvate!”, casting healing word on Burr.  

Toll the dead : DC 13 wisdom save or take 2 necrotic damage on the pack of rats.  

Healing word : healing Burr for 5 hit points of healing.  

Interspersed with his surprise and alarm at the rats' sudden ambush of Burr, Soren feels a tiny thread of relief that something is alive within the house.

Feeling mostly drained of his own primal magic, he feels much greater relief when not-father Giles calls on Tymora's divine healing to revive the bigger man.  Keeping a clear view of Burr and the rats through the doors, Soren steps back (north) five feet, holding his small wooden shield in front of himself as a mass of thorny green vines forms within his free hand.  Lashing out, he tries to scrape the rats off his companion, pulling them towards himself.

Soren's Thorn Whip on the rat swarm from 20' north of them:
To Hit:  14
Damage on hit:  2 magical piercing
Forced Movement on hit:  swarm of rats is dragged northward ten feet (scraping them off Burr), aiming to give Burr room to stand up and separate himself without having to disengage.  If successful, rat swarm ends up next to the door, 10' south of Soren (5' south of his prior location).

"If you can, do not stay in one place once they swarm you," Soren calls out.  "These are animals whose attacks depend on close-range swarming as a pack.  Disengage and move away if they jump on you while everyone else continues to whittle down their numbers."

Burr had the curious sensation of being eaten alive then reborn as from a seething womb of teeth and matted fur.....it was not pleasant.

Dragging himself to his feet he unslung his maul and advanced on the swarm, " Payback."

Attack: 14 Damage: 10

( Or not...)

The twang of the harp string surprises Zefla, but not as much as the shout from Burr as he is attacked.  As she turns around, she watches in horror as he goes down, covered in a swarm of rats.

Luckily, Giles is able to assist him and once Soren attacks, whether or not the swarm is moved to the North, Zefla unsheathes her shortsword and dagger and rushes the rats.  "Gaaah!!" shouting a halfling warcry :)

Attack: 24 Damage: 8

Attack: 19 Damage: 7

If the thornwhip didn't work, she'll get sneak attack:  1 added damage if she hits

The rats are unfazed by Giles' spell; these vermin care not for whom the bells toll.  Soren's Thorn Whip is more effective.  Though is only grabs part of the swarm, the rest chase after their brothers, sisters, cousins, and other more complicated relations, and reform the swarm closer to the door.

Burr, perhaps still shaking by another brush with grisly death, is woefully off with his maul, nearly smashing poor Zefla as she darts in to attack.  

Of the foursome, Zefla is most effective, stabbing with both blades and skewering rats left and right.  The mass seems appreciably smaller now than before.

Retreating from the crashing doom of Burr's maul, the Rat Swarm turns to Zefla.  The much smaller swarm finds a target to match, moving into her space and crawling up her pantlegs and leaping to bite at her fingers.

Attack: 13 Damage: 6

ROUND TWO

1. Giles
2. Soren
3. Zefla
4. Burr
5. Swarm of Rats

Giles recoils in horror as Zefla is covered in rats.  He points his hand at the rats and another sound like a gong occurs, hopefully frightening the rats.  

Toll the dead on the pack of rats  : DC 13 wisdom save or take 6 necrotic damage.  

As a bonus action, he will use his telekinetic mage hand to swipe the rats off Zefla.  DC 13 strength save to resist if applicable, he’s trying to knock them off her body, push them away.  

Soren's Thorn Whip lashes at the swarm of rats once more.  Trying to scrape them off Zefla if they are not already off.

To Hit:  14
Damage:  2 magical piercing (Soren chastises himself at his repeated inability to make much of a dent in the swarm).
Forced Movement:  IF the rats are still on Zefla, Soren pulls them 5' towards himself.

He makes sure that he finishes his turn within 5' of the rats to provide distraction for Zefla's sneaky metal claws.  Shield up.

Burr moved over, " Zefla duck!", he brought his maul down on the rats.

Attack: 13 Damage: 11

This time the rats do hear the tolling of the Bells of Giles, and their little minds can't handle the sound.  Many fall off of Zefla, and more yet are ripped off of her by Soren's thrown whip, pulled out into the hall.  Burr charges in, maul swinging, and obliterates the last that had any fight left in them.  A handful of survivors rat-hop away into the corners of the room or up the stairs, with one dreamer attempting to take wing out the open window of the Conservatory (the music room you just explored).

Quiet returns to the house, other than your labored breathing and the muted dripping of rat gore into the space between the floors.

[Burr and Zefla, CON saves please.]

Zefla CON save  18

Zefla rubs at her fingers that are now full of little rat bites, and looks to the others, "Thanks.  I think I'm done with this room."

And she turns out of the conservatory and goes to open the doors across the hall.

"Our health and magic are weakening with all the fights we have had, starting with the goblins, then the werewolves and now these rats.  I think if we can confirm that this level of the man-den is clear, we should take a rest, perhaps for the night, before continuing higher up the stairs."

Soren nevertheless proceeds behind Zefla and calls for Silvanus' Guidance on her as she goes to check the northern room.

“Agree with you there.  It seems like so long ago, we gathered to hunt werewolves…. and look where we are now.  I need some rest….”  Giles looks around, following Soren.  

Zefla just can't help but continue to explore.  She pushes open the double doors across the second floor hall and steps into what was once a magnificent private library.

The dusty ruins of red velvet drapes hang over the windows of this room. An exquisite mahogany desk with locked drawers and a matching high-back chair face the entrance and the fireplace, above which hangs a framed oil painting of a windmill perched atop a rocky crag. Situated in corners of the room are two overstuffed chairs. The walls are covered in expensive-looking two-tone red and black wallpaper. 

Floor-to-ceiling bookshelves line the wall opposite the fireplace. A rolling wooden ladder once allowed one to more easily reach the high shelves.  Now, that wall sags noticeably.  The bookshelves are waterlogged and most of the collection are nothing more than mouldy pulp now.

Con Save: 16

" This place looks secure. Lets barricade the door and have a kip."

Giles heads to the bookcase, looking for any books that remain undamaged, readable.  When Burr speaks, Giles agrees with him saying “I could definitely do with a rest.  Do any of you have a way of securing the door?  Drive a piton into the wood in the floor?”