Hello  from the UK, were most cats live inside and out...
I have 2 cats one Tabby and white Male
Mozzy and a very posh lady Tortashell called Mr's Tilsley or Tilly on a good
day. Both are 'reclaimed' strays Mozzy appeared just after Christmas 3 years
back, sat on my door step one very wet night, I opened the door and in he
came, ate my corned beef and fell asleep in front of the radiator. I put an
add in the shop, no one came for him so I took him to the vet for the
snip. He was scanned /chipped and is up to date with his injections. Tilly
was another abandoned cat, left behind I suspect when some one moved. I saw
her in a cage in the cat shop, was told she was a bit nasty. I picked her up
no problem and she purred right away, so I bought her for £25 from the
cattery/cat shop. Took her to same vets for scanning/ chipping.
Now we all live together 'happily' in my little flat. Well we did, until
this big old boy moved into the vicinity.
A lovely big black and white male ( most everyone else who sees him thinks
he looks like a retired alcoholic boxer!)
To be honest I was a bit naive in the situation. I sarcastically though
great! Another stray to keep an eye on and for about 2 months he sort of
hung round the far end of the yard. I could never get close to him but saw
him eating the grub I put out. Then I let him see it was me feeding him,
moved the food closer to my shed. After a while he moved in the shed, then
one day he came up to me. He was bald scabby no weight on him even though he
was getting a good portion of Hills every day and water. I set a trap using
a cat box and string and caught him, took him to pet smart vet, (I have
changed to pet smart) he said he had flea's, Eczema, worms, the lot. I got
him treated told the vet he was stray but I would give him a chance at my
house. Vet said he can't give any discount, but gave me a big bag of
assorted samples of food, and I brought him home.

That's when he set about Mozzy and Tilly, talk about aggressive!  We stuck
it out a week or two but all he wanted was out, or a fight, he was getting
very 'nasty' with M&T, his fur was mostly back, and he had put weight on as
he was wormed, the better he got, the nastier he was.
So to be honest after one bad scrap, I just let him out.
Off he shot, I didn't see much of him for a couple of weeks. Then he started
hanging around again, so muggins started feeding him. Well he's back proper
now, scabby again to boot. I suppose I invite him having started to feed him
again, now he sort of hangs around the back door attacking my two cats when
they walk near him. Poor Mozzy stayed out the other night, I went looking
for him and realised Mr Stray was guarding the cat flap to stop him getting
in, Mozz is sat right up the end of the garden looking sad.. Tilly's a big
girl so he doesn't get away with much in respect of her, but Mozzy's life is
a bit miserable at the moment. I didn't believe my own eyes on Saturday when
the back door was open Tilly stated having a hissy fit and went to look, I
found stray cat crapping in her tray, indoors. Cheek or what? He has never
done that before,,, I don't think.

So can you advise with this kind of thing? I don't want any harm coming to
Mr
Stray/ Batcat (he looks like Batman in his mask) One to one he is a really
nice cat, if I sit in the garden on my own he will put himself in my lap and
purr like a happy thing. If he sees my other cats he goes wild. I have even
got front line on his neck, so he has no fleas, but I see his Eczema is back
this visit. To be blunt I gave it a go, my other two are being made to feel
unwelcome and they were here first. I already gave the vet £70 to sort him
out last time, I know its not going to be cheap for his injections. If you
can help with this old lad? I will entrap him again using the cat carrier
box and string trick, transport him to a proper establishment and give cash
toward his medication.
I trapped him a few weeks ago and took him to a very dodgey (in my opinion)
place in xxxx xxxxxxx where they wanted me to sign a humane destruction
form and leave him at their mercy. I really didn't like the look of the
place so I brought him back. I think we managed 3 days before he made a
break that time.

Righty ho I hope to hear from you, with some helpful suggestions all the
best