Allagan Tomestones are a currency acquired through high-level duties, the Duty Roulette, Beast Tribe quests, The Hunt, Treasure Maps, The Diadem, and PvP. They can be spent at Auriana to purchase various weapons, armor, accessories, and other misc. items.
There are three types of Allagan Tomestones currently available:
Prior tomestones are no longer obtainable and have no use, but may be exchanged at Auriana for newer tomestones at a 4:1 rate:
Older tomestones have been completely removed from the game: