Now this solution has been done in the games Warframe and Destiny 1 and 2. We know it, we love it, Weekly Legendary Merchants from far off places. Here is my attempt at it.
The merchant name would be a Wizard in some gear similar to basic wizard city gear with special hair. They would sell Ultra-Rare Jewels for a new resource, Crown Shards. The Shards can be farmed from All Final Bosses from each world, giving more based on Boss Rank (Rank 1 gives 2 Shards, Rank 15 gives 30 Shards), guaranteed of course. The Kroger Jewels would rotate out 2 at a time, along with new maycast jewels added in. On top of this, this Merchant will give various items, each looking grand and fantastical.
These Prices can change but they cannot be so over the top that it would be impossible to get at least 1 thing a week but not to low as to allow farming early world bosses to be easier/quicker. This is to incentivize farming end world bosses for more then just their drops, thus adding more play time. These shard bought items can be stitched For free as to allow people to grind for fashion that they would enjoy.
The ability to grind these shards out is in every game that allows such a character, on top of this though, if the dropped amount is to low, then you would horribly fail the implementation.
I forgot to add Calculations for gaining say a permanent spell within a week.
Assuming your Max Level Farming The Trident, a rank 15 boss I believe, will give 30 shards per successful run. You'd need 1000 for a new spell. So you would need to farm the Trident about 35 times throughout the week to gain a new spell. Harsh, yes. So lets look at how long that would take you on average.
5 Days before Merchant Arrival, 35 Trident Runs, 1000 Shards needed, 30 shards per run.
7 Trident Runs a Day to gain 210 Shards for that day. Over the week, you'd gain 1050 for a new spell.
Kroger Jewels? Even easier. 1 Trident run a day for all 5 days will get you nearly enough to gain both Jewels available that weekend.
An issue that can arise is "What if a newer player sits down and farms out Lord Nightshade? They would have an overpowered maycast at hand atleast once a week!'
Well yes, but for a new player to ALSO have an Ultra Pet to slot those Jewels onto at the same time? Lord Nightshade is a Rank 3 final boss, meaning he would drop 6 shards. For a new player to get 1 Jewel from our weekly merchant, they would need to grind Lord Nightshade 17 times. Lets Calculate for a new spell as well.
This new player would need to farm Lord Nightshade 167 Times throughout a 5 day period to gain a new spell. Yes they can just team up through this, but this is to offer an alternative way for Kroger Jewels, New Fashion, New Equipment, AND Loremaster Spells to be gained, which would reward play time, dedication, and willingness to slaughter through such a grind for these things.
another good idea that would not only benefit kingsisle but the players as well is if we were able to buy the jewels online like we can with the bundles on this main website it would not only get kingsisle more money but people would be able to get kroger jewels which is near impossible because not only are kroger stores so hard to find its not really the best place to sell them at and the same goes for walmart too they are both not selling any form of wiz cards and even if they did they have a very bad issue with activating cards i lost 40$ because of them (and yes i went back with a reciept they still refused to activated it AND the only emails kingsisle gave me was the usual "give us a screenshot and the number on the back and such" neither side did anything to help but aside from my issue i really think it'd REALLY be better if the kroger jewels be it the 10$ or 20$ ones they would be better off being sold online on this website