These recently appeared in my house, I've been there for almost a year and only now have they appeared.
(I don't know if it's because of the heavy rains in my area)

Here's another image

Need more information. Is that your basement?
Does your yard slope towards your house.
Do you live on a slab or crawlspace?
Don't use any water; note the number on the meter before you go to work, and note it when you get back; did it increase?

>>2919707
It's in my living room.
>Do you live on a slab or crawlspace?
I live in an apartment
>Does your yard slope towards your house.
No

>>2919703 (OP)
Mayby just put a fan pointed to the area to dry it out before it goes moldy

>>2919710
I'm going to try it

>Update May 29
started appearing in my room

Looks like "rising damp"

https://www.youtube.com/watch?v=RbyaRgkfhwg