These would come in various sizes ( 5k, 10k, 25k, 100k) and types (adventuring, crafting, both). The lowest level ones could be sold to a small number of NPCs. Their use counts towards attenuation (e.g. would not violate the experience per hour limit). They a rare drops and would be trade-able. They could also be combinable at a cost. e.g. 5x 25k ones could be combined into a 100k Elixir. One benefit for such an item would be as a daily reward on QA. These would be an item that legitimately exists on the production server with a designed purpose that could also be freely handed out on QA so new/higher level skills could easily be tested.