Magical charge (Teleport charges)
My suggestion is an item (Magical charge as a place holder name) that can be used on items that grant teleports and have charges (eg. Morytania legs, Ardougne cloak, Fremennik sea boots, Pharaoh's sceptre, etc.).
This item would grant the object it is used on another teleport charge, allowing the owner to do things like teleport multiple times a day to the Rellekka market with the tier 3 boots, more than 3/5 daily teleports to the Ardougne farm path with the tier 2/3 Ardougne cloak, or charge a Pharaoh's sceptre without needing artifacts and the mummy.
I do not see this devaluing the elite tier rewards that grant unlimited teleports or traditional ways to recharge items. This would be a convenience method that would have a GP or time cost associated with it depending on the method the Magical charge can be obtained.
I can see the item coming from a low to mid-tier boss, mid to high-level slayer monsters, or a new magic/runecrafting/crafting method. If you really wanted to get creative, perhaps it could come from a gathering skill like mining or fishing and require some processing to make the tradable item.
Magical charge would help with items that have too few charges to be useful, such as the Fremennik sea boots, and with items that have difficult or inconvenient recharge methods that a player may want to pay to circumvent.
11-Jan-2022 18:01:19