My suggestion is to have an item called “Eternity Sanctum Key of Memory” that allows us upon use to skip directly to the Eternity Cache of that dungeon equal to the highest level that we have already defeated. So if you’ve beaten Eternity Sanctum level 3, you can access the Cache (only that last room, nothing else) at level 3.
Or highest level - 1, if people think that’s too generous.
Or just allow access to the Eternity Cache from the map, once you’ve accessed it at least once. (I.e. put a teleporter in the room.)
The purpose of this suggestion is to make attempting a legendary craft take about ten less minutes each time. Thanks for reading and please upvote if you like this idea.