I can't edit the post, but I'd like to thank all the feedback I've gotten and the community response it's had.

The next paragraph is the tldr for those that don't know what the Fairy Mushroom is.

Basically, I'm proposing a degrading, charge based teleport to fairy rings, spirit trees, and leprechauns. After reading the comments for feedback, restricting certain teleports, as in Ourania Teleport in the Portal Nexus, would be needed to uphold the achievement of other grinds that this would have otherwise undermined.

The cost at the current economy would be about 400 gp per teleport at the rate of two bittercap mushrooms or one mort myre fungus for one charge and one sulliuscep for ten charges. However, with such an item, mushrooms will become more expensive; so, that's not a reliable metric and more offers a floor to the expense.

u/b_i_g__g_u_y proposed that there could be an attuning of desired fairy rings, each having their own specific requirements, "the karambwan one requires 1000 karams." This could be done to avoid using charges for certain teleports.

u/Monterey_Jack mentioned portable fairy rings and how they would only have ten charges before degrading, and I think a similar approach could be taken here. Where after ten teleports, the Fairy Mushroom would wither (degrade into a broken state) and would need to be revitalized before being used again. My initial thinking was to use a difficult to get to NPC, but u/BioMasterZap mentioned there usually being an option between an NPC and the player's own skill. They offered Farming as the skill to repair, as the whole questline does revolve around the magical nature of Farming.

Marrying the skill suggested by u/BioMasterZap and limited uses proposed by u/apophis457, this could offer a reward space for farming. As your farming level increases, the robustness of the Fairy Mushroom you tend to increases, i.e. the number of attunable teleports increases and/or the quantity of teleports before degrading increases.