MAngband

Is it feasible (or desirable) to have potions of invisibility, or even items that grant invisibility (a plain gold ring, perhaps?).  I remember items like this in ToME and Nethack.

I've strongly considered that.  Especially potions that would make you invisible to other players.

Such things might not make you invisible to everything, though, so a new attribute would be needed for monsters (SEE_INVIS), as quite a few of them can.

Note that *being* invisible does not mean you can *see* invisible.  This might have the effect of rendering you incapable of reading your own books, or wielding a weapon/shield with any skill.

That might make a {cursed} Ring of Invisibility a real nasty "gift" for a newbie player.

Yah, well, the same is true about tele rings and amulets, so I don't think that's a problem.  At least with the invis ring you could get back to down and get a remove curse before starving to death since you couldn't get near the shop .  And really, if you put on an unID'd ring you deserve whatever happens, in my opinion.