I have found these under every tavern I come across!

I've found them in most town halls as well.

The funny part is that they're very similar to deceased giant rats, so in my session this friday, i'm featuring a tower that has giant rats, and what creatures they are will depend on how nice to me the players are.

OKay but how big is it actually? You can't just say Size Category and expect that to work. 

RATS, WE'RE RATS; WE'RE THE RATS. WE PREY AT NIGHT WE STALK AT NIGHT WE'RE THE RATS

Quote from RosslynPaladin >>

OKay but how big is it actually? You can't just say Size Category and expect that to work. 

  
Smaller and much weaker than a mastiff but with higher hp. I'd say about 2.5-3.5 feet long minus the tail, 30ish lbs but with some flab on it usually.
Anyone else think the mastiff should have more than 5 hp?

Dio would argue otherwise.

Has anyone seen a homebrew for swarm of giant rats?

Size Small is pretty crazy for a rat when you consider it the same category as Halflings and Gnomes. A cat in D&D is typically size Tiny. Dogs range from Small to Medium depending on the breed.

Using it in my campaign and had too change my town to a city =/

It makes all of the rules.

Quote from RosslynPaladin >>

OKay but how big is it actually? You can't just say Size Category and expect that to work. 

 Small Creatures range are about half the size of Medium creatures. An example would be that these rats would be about the same size of the average dog IRL. Hope that helps.

I adopted one in my recent campaign. His name is Renald :3

I tamed one of them with my character who was named Raslen so I named it Ratslen now every campaign I go to I have a pet rat that likes to sit on my back.

when i dm i consider it the size of a dog

I tamed 2 of them and they are now my army

I think they are about 2-3 ft. long ignoring the tail.

R.O.U.S.'s

Rodents of Unusual Size.

"Small" is the size for a "Giant" Rat.  Gnomes and Halflings can ride this size creature . 

fight