Used to teleport to previously cleared levels in Nyzul Isle Investigation. You can also use tokens to get items from a vending box in the lobby of Nyzul Isle Investigation prior to selecting a floor.
Tokens are tallied automatically and do not show up in your list of key items. You can check how many tokens you have with Sorrowful Sage, or with the NPC standing outstide of the Runic Portal of the Nyzul Isle Staging Point.
You gain tokens by completing floors in the Assault Mission Nyzul Isle Investigation and successfully leaving using a Rune of Transfer before time is up.
If you are on the quest Duties, Tasks, and Deeds, Zasshal will offer to sell you the Wyrmseeker Areuhat for 150,000 tokens.