ToME WikiI have mimic skill over 35, and have been using an artifact magestaff and artifact shield with it. When I went up a stair, that exact turn I lost my extra arm. I assume it isn't a bug that they drop to the floor instead of your inventory, I don't have an issue with that. But they dropped after I hit <, and I was on a new level before I could possibly pick them up again. I don't know if this is a bug or not. My guess is it isn't and it's just tough luck. I use artifact items because if you're in trees or whatever and it happens, they get thrown somewhere on the level. So my question is should I post this as a bug in the appropriate place?
NeilStevens: It is tough luck, unfortunately. May I suggest you use the option to confirm when leaving a level?
Derakon: How would that make a difference? If he doesn't confirm leaving the level, then no time is taken, so the arms do not fall off. If he does confirm, then time is taken, the arms fall off, and then he leaves the level. This seems like a flaw in how movement between regions is done; anything that affects the player's state should happen after appearing on the new level.
MrConceit: Yeah I think Derekon is right. The only "resolution" if this is the way it's supposed to operate is to take the stuff off before using stairs just in case RNG has it out for you that turn. I am a deathmold, and could also use deathmold abilities, except I can't in Angband, where I am. 
That's a foolproof way to not lose your stuff, but it's also irritating. Since the most common stuff for me is plus to mana or life, and thus you have to rest on the next level after reequipping. So I'm curious if the final word is "This is how it's supposed to be" or not. Thanks for responding so quickly btw.
NeilStevens: This is fixed another way in ToME 3: you can check the ! screen before you leave a level, to see how many turns you have left of the timed effect, by the way.
Atarlost: It should not be possible for mimicry to expire while changing climing stairs or changing wilderness zones. Neither takes any time in game terms. *looks at the source* It looks like, because of the way leaving a level is handled, the world gets processed even though no energy has been used. To fix this make the line where process_world() is called in static void dungeon(void) include a check for p_ptr->leaving.
MrConceit: I figured I should post here what somebody told me on the forums in case somebody else is worried or experiencing similar problems. You just need to recast arms periodically and it resets the timer. Specifically you can cast it right before you use stairs and never have a problem. If you do it correctly you will _always_ have the extra arms and they will never fall off.