Item description:

Silver - Serpent Savior - Freed 120 Bound Serpents
There is a map attached, simply drive to the last green icon on the map and free the serpent.

Silver - Loyal Customer - Purchased all upgrades in the Motor Forge
Drive to any motor forge and buy the last upgrade.

Silver - Favored - Acquired 3,000 Fire Tributes
This unlocked when I discovered the final vista. There is a map attached, head to the yellow icon.

Bronze - Now You Must Tell the Tale - Viewed all Legends
Drive to the purple icon on the map to unlock this trophy.

Bronze - Voices From Beyond - Unlock all songs in the Mouth of Metal
Drive to the last musical note on the map attached and the trophy will unlock.

Bronze - Tourist - Viewed all vistas
Use the attached map and drive to the yellow icon for the trophy.