Legend Tablets are gained randomly from completing Treasure Maps, they are a semi-rare bonus intended for players to collect. There are ten of these tablets in all, one for each of the ten legends.
These tablets can be placed inside a Museum room, the museum room/building deed is a drop only 5000 skill construction plan.
The room can be used to show off your collection, you can furnish the room and add the tablets to it. When you click on one of the tablets in a furnished room it gives you a small story detailing the Legend exploits of the person the tablet represents.
As they are collectible items, other players may offer a good amount of money to buy them.