The card says, "Once per turn,… [paraphrasing] you may look at the top exploration card of your room." It says "Once per turn…" [not paraphrased], so can I do this once per investigator per round, plus the Keeper's turn because there seems to be no active turn restriction?

For instance, at the start of Michael McGlen's turn (who is completely on the otherside of the map, far from Monteray's room), I look at the exploration card underneath Monteray Jack and find it's a Nothing of Interest and put it back facedown. Monteray Jack then takes his turn when McGlen is done. Monteray Jack decides not to explore knowing the card is useless and moves into Bathroom 2, does his Legacy Map again for his turn and sees it's a Lost Soul card, moves again to the Chapel and moves once more as his action, still in the Chapel. The Keeper starts his turn and before anything else, Monteray Jack looks at the exploration card in the Chapel and sees its an Elder Sign, and places it back facedown.

Again, is this a legimate use of this map's ability, seeing as it requires no action to perform nor limits when it may be activated?

It has limits. The limits are "once per turn." You're using it 4 times per turn. Once per turn means you may use it once during Monterey Jack's turn.

My example is legitimate because all those turns are taking place over a single round, which is the crux of the dilemma. The Legendary Map is limited only by turn, not round, and because it does not use an action to activate, it would seem it may be activated on anyone's turn but only once each.

I believe what I should have asked is are investigator abilities and investigator cards restricted to only being used on their own investigator turns unless specifically stated otherwise? The answer would clarify outright the Legendary Map ability by a universal ruling that overrides it's broad text.

Yes, you may only use this on the turn of the player who is in possession of the item.

Musha Shukou said:

One of my players is the one who found out the map trick. Do you have a page in the rules I may reference?

One of my players is the one who found out the map trick. Do you have a page in the rules I may reference?

This is not a trick, it's a cheat. Just read through the investigator turn in detail on page 8-- it says nothing about doing stuff during somebody else's turn. But I don't believe that the exact situation you're looking for is described in the rulebook; it's just common sense. You already know what the intention of that card is. If you or your friends want to find loopholes or intentionally misinterpret how that card is meant to be used, it will grossly weight the game towards the investigators and make the keeper angry. But, house rules are house rules. Go ahead and play it as you wish.

It's referring to 'you may'… which means current active player who has the map….

Ohterwise base on your thought, you could also break the limit of Mytho cards and many other things.

As rule book says Mytho cards is played per investigator per turn . But obviously it's targeted to the current active investigator. Otherwise, you may concentrate 4 Mytho cards on single investigator.

I think the reason why it's not saying per round is beacsue in future, some effects will cause investigator perfom more than one turn in single round. In this case, 'once per investigator per round' and 'once per investigator per turn' will be totaly different.

My take: The legendary map is a card . Using it is a Card Action. An investigator may make one Card Action as part of his/her turn.

The rules bods need to get a bit more rigorous in their dictionaries of terms. In the old days the turn would be split into phases. refering to the "investigators go, keeper goes" part as a turn and breaking that down into "First Investigator Phase, Second Investigator Phase, Third Investigator Phase, Keeper Phase" would have made it a tad clearer.

Using the map is not a card action. It is automatic.

But I agree with most of the posters here: it can only be used on Jack's turn. So, in essence, the map is usable once, by any player, per game round.