With the latest Prestige Update a few weeks ago, you implemented new Items to upgrade the stardom of Monster Cards.
This was a great idea.
As I saw in the possible loot list, there are several items, and in general they grant a jump to a certain level of stardom, like jump directly to 4 star stardom.
My suggestion is to introduce another item that grants to add one star to the stardom. So if the stardom is 4 you can advance to 5, if it is 3 you can advance to 4.
Reason: If I use the "jump to 3" or "jump to 4", i will still miss a step, and should rather wait and use "jump to 5", which makes most of the items not extremely useful for me.
So, having the opportunity to get just one star would be a great complement to the set of items you implemnted.
Second suggestion:
You culd make these items available in the mirrir-shard shop, as this shop has mostly outdated items at offer, and recently the mirrorworlds git added to the new card system.