Slugs usually come into your house at night for warmth, shade or even food etc.
The Yellow Cellar slug mostly eats mold and algae but can also be found eating leftovers, pet food and compost.
Slugs including the yellow cellar slug also is attracted to dark damp refuges such as vents and drains so make sure to remove any standing water and get rid of dampness around your house.
You can use salt to kill slugs when they come into your house.
Just pour some regular table salt onto the slugs body and the salt will dry out the slugs body and dehydrate the slug which causes the slug to do.
The salt slowly kills the slugs and it's a safe and natural way to kill slugs.
Putting some Epsom Salt around areas where the slugs come inside can also help repel the slugs.
Also check for where the slugs are coming in and seal any holes or entry ways for the slugs so they cannot get in.