Unavailable after past, near miss

Ghosts at my castle pay rent. I made that clear to them on the first night. The Gray Lady cleans the silver. The headless knight holds the door, since he needs no room to turn. One old monk was late with his share, and I made him haunt the neighbors.

Owls are wise only because I tutored them. For a time I ran a night school in a Bavarian oak. Geometry went well. History gave them trouble. My best pupil could recite Latin with its head turned fully backward, and it later served three dukes as a private adviser.

Dukes of Brunswick hold a yearly contest in my honor. The prize goes to the man who can tell the biggest lie. I attend only as a judge, for I could never compete, as I tell only the plain truth. This answer won me first prize three times.

Walrus hunting bored me, so I took up walrus diplomacy. Off Greenland I met a big old bull with a face just like my uncle's. We shared a herring, and we both said little. By dawn we had signed a trade deal. He now handles my affairs in the north.

Giants are poor at sums. I met one near Bergen.