This current suggestion is meant to be combined with the one here.
Link to my previous suggestion:
I like Gnomes, but they are not useful in any battles, except for the trolling purposes.
Getting one card of any Gnome will allow you to level it to the max level 15.
However, if you ascend the same card 6 times, to Mythic status and level 20, there should be more done to it than just increased statistics.
Values are not additive: (increases in %)
Common: Level 15 (white) - default value - chances stay the same.
Rare: Level 16 (green) - increased chances to appear more frequently (+1%)
Ultra-Rare: Level 17 (blue) - increased chances… (+2%)
Epic: Level 18 (purple) - increased chances… (+3%)
Legendary: Level 16 (orange) - increased chances… (+4%)
Mythic: Level 20 (cyan) - increased chances… (+5%) - maximum