Proposing a new gamemode called trials.
Similair to the gauntlet, except level progression is permanent and the oponents are fixed.
While the gauntlet is based on making a durable team, the trials would be more about how well you can team build for ever stronger oponents and countering specific synergies with clever team compositions.
Perhaps certain levels would have special conditions like "hold out untill round 20 with a full team" or "beat the oponents in three turns" for say every 10 increments. (stage levels would not be tied to oponent levels.)
Only issue is people without KS/beta companions are at disadvantage.
Maybe you can acquire trial only mirrors through progressing on levels.
Also team composition would have all your familiars at their level available, same with your wolves.
You can use a companion as many times as you own it. And as many wolves as you own.
You would get a reward only once for a level.
And you can rematch older levels.
Ever increasing or challanging levels can be added down the line as old ones are figured out