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No, it's not complicated, just time-consuming. I wouldn't have enough time for it, at least not this week. And my creatures are different from those in the pack.
Here's another interesting point.
No matter what level a creature is, in battle, it will be capped at 8, and the player will see a maximum of 8.
But - a level 9 creature cannot be summoned. As soon as you reduce it to 8, it's okay.
I tested it with a Hellspawn.