Teleport can go wrong even when you are very familiar with the destination, but if you have an associated object, you can arrive at the right destination with 100% certainty.
The spell describes an associated object as follows:
"Associated object" means that you possess an object taken from the desired destination within the last six months, such as a book from a wizard's library, bed linen from a royal suite, or a chunk of marble from a lich's secret tomb.
But what does taken from the desired destination imply about how long the object must have been there, if anything?
Technically, everything the wizard has on their person has been in any location they visited in the last six months, and hence has been taken from there. Does this mean the wizard, as long as they do not change their clothes, shoes, spellbook or whatever object they carry with them, can safely teleport to any place they visited in the last six months? Does it mean if the wizard receives a letter from the king, he can teleport to wherever that letter was written? If not, what can reasonable criteria be?
It's clear from the examples, that the object does not need to originally be from the destination. The bed linens were certainly manufactured somewhere else and then transported to the royal suite, and they might be changed daily.
Obviously, the DM can make a ruling on this, but is that all? What are your experiences with ruling on this, and how well did these rulings work?
Best Answer
When the DM says.
As you noted, the teleport spell says:
Exactly what that means, in all its nuance, is just not specified in the rules. In the end, it's more a question of adjudication and world-building than anything else.
As a player
You need to work it out with your DM.
As a DM
You can homerule this however you choose to interpret it, to whatever depth satisfies your homeruling and worldbuilding desires.
"Reasonable criteria" probably cannot be defined outside of a specific game, because what works for one table may not work for another.
We have used this aspect of teleport extensively and have never had any issues.
Some rules that have been successful for us:
Teleporting with an object to its associated location "resets the clock" for that object, as much as to save us the tedium of saying things like "I drop the rock and pick up a new rock" as anything else.
Objects can be incredibly mundane, such as a chip of brick, a leaf, or a pebble.
Someone else can bring you an object and you can use it as an associated object.
We have only used objects intentionally acquired as a teleport object, although we haven't specifically made a rule. As an example, even if using an apple to teleport to the tree it grew on is legal, we have not explored using teleport in that way. Although if someone specifically picked up the apple to use as an associated object and brought it to the teleporting wizard to use as a teleport object, that would be consistent with our use. While that could probably be reduced to a rule, we have not yet had the need to houserule it.
We briefly discussed the idea that everyplace you go any objects in your possession are suddenly "from" that place, and discarded it as patently absurd, without exploring reasoning or exact mechanics in depth.
Most DMs can probably successfully handle it at their own table by building up rules that work for their game in a similar way.