There are 50 legendary weapons in the game, but only you can obtain only 30 of them yourself with one hero. To collect them all, you'll have to complete the game a couple times or exchange with other gamers through Xbox LIVE!, as each character receives a random package of weapons/ The weapons can be bought at the blacksmith's in a couple cities in Albion or found in the locations listen below.
Exit from The Hole, cross the first lake and you will reach a small bridge. On the other side, on the left, there will be a small hill. At the top there's a chest requiring 10 silver keys and inside a legendary weapon.
Inside the chest in the middle of the path leading to the fortress.
Inside the Ossuary, behind the door requiring a gold key.
Obtain 5 million gold, step onto your treasure in the Sanctuary and pick up the key hidden above. It will open the chest beneath the gold pile. To reach it, spend or transfer all your money to the castle. Inside the chest you will find the legendary weapon.
Complete "Gnomes are Evil!". In return you will receive the legendary rifle.
The weapon can be found behind the door requiring a gold key.
City of Aurora
The first weapon has been hidden behind the Demon Door and the second inside the chest (20 silver keys) in the temple.
The weapon is inside a chest requiring 50 silver keys, which has been hidden in the castle garden, to the right of the entrance to the Catacombs.
The weapon has been hidden inside the chest requiring 20 silver keys, which is behind the house in front of the Demon Door.