More of what might have been said
Yes, he is a halfblood and a monster. He is also the tutor engaged by Lord Black for the Viscount Potter and you will welcome him accordingly. Kreacher, you are doing admirably in tidying up the house. Lady Black, Lord Black wishes to remind you that he finds this conduct utterly unbecoming of one of your breeding and does not wish to have to reprimand you about your language again.
The Viscount Potter's tutor has a lot to do in a short time. Servants of the house of Black have resided here before, and will again. Please do the family the honor of making him welcome.
There will be a team of warders calling by later in the day to check the house for objects that might pose a danger to the young Viscount when he is finally able to visit, and to make sure that the family wards are still strong. Kreacher, please have all artifacts and mementoes that are made up of pieces of sentient or semi-sentient creatures moved to dungeon number three before this time. If it pleases you to arrange them as a museum, you may of course do so.