@JonSM:
"have a tough retrieval" as my first instinct would mean it has a high coefficient. But since you already dismissed Tuber's Bag, and no coeff.6 item seems to fit, it must mean something else. So either:
(1) Somehow it is hard to pick up when it appears in the game (probably because it could turn out badly and you have to hesitate and think about it).
(2) It is hard to unlock in the first place because of a difficult quest.
Going off (1), I would think

, because its maker (Sauron) is indeed the evilest there is, and on certain levels its effect could be valuable to you. I fail to see, though, how it helps out with sports.

and

help out with sports, but they don't seem to fit the other clues (in particular "my maker, very evil").