What do you think about this: "Gods"
Primals are fun. Coil is nice. Can't wait for the new primals and the new turns. New content always makes us happy (for some people that happiness lasts about 1 day xD).
But how about we can do coil (and maybe primals) to gain access to "Gods". I'm sure the lore fanatics can come up with a better name, but Kirin came to mind and he is a God to me in the FF series.
How would this work: 8 people clear turn 6. Those same 8 people will (automatically) gain a crystal or token or whatever fits the lore. This item will grant these chosen 8 the power to fight Kirin, roaaaaar!
Kirin only spawns once every X hours. However, to avoid all claim-botting, Kirin randomly chooses one player. The other 7 members in the party can fight Kirin together with the claimed player. Should you down him, you'll have to wait to do turn 6 again to get access to him again.