Can anyone identify this Eldritch Horror in my windowframe?

[AnHorribleThing]

I've just looked up and seen this Thing in the top corner of my window, I have no idea how long it's been there for.

Does anyone know what it is/how toxic it might be/whether I should stop being in there until I have a chance to get it looked at?

Looks like some kind of slime mould. Is the wood damp? Not sure about cleaning it off though sorry.

Saisong I think it has eaten its way in from the outside but I'm not sure if the bit inside is actual fungus structure or some kind of degradation of the foam insulation. I touched the beige bit (very gently) and it felt like the cap of a mushroom.

It does look fungus like. If I was you I'd scrape it off, whilst wearing gloves and a mask (proper dust mask if you can). Then treat with dilute bleach and get some good ventilation going in that room. Once it is off you can see the condition of the plaster/wood - it may well need treatment, possibly by a professional.

Is it dry rot

I found this page, and some of the dry rot growths look a bit like yours - I'd get it checked out
gullivertt.co.uk/gallery/timber-and-damp/

Definitely mould if some sort. As pp have said it may need professional action.

I’d be tempted to burn the house down and run away, but I know that’s possibly a tad extreme.

Thank you all, I've never seen anything like it and was very alarmed. Will attempt to get property manager on that ASAP.

Ohhhh. It looks a lot like dry rot. Bad news if it is. Hard to treat and expensive. Is it a rental?

funder it is a rental rather than my property.

AdoraBell doesn't sound extreme to me at all. There is something GROWING in my room!

Nasty
Are there wood joists and floorboards?
It may have eaten away underneath the floors too
Can you pull up carpet or boards?
How long is your ren tal for? Is it long term
You might be forced to move out if is widespread

(One place I rented the dry rot was everywhere..Once they looked....under boards etc .... I found new place rather than rely on their insurance finding me some where temporary

Embracelife we've had a look at the room above and it looks OK but who knows what's going on under the floorboards

Look under the floorboards at all the joists

My guess would be dry rot.