Owlbear Shepherd's ability has an intervening if clause, which means that it checks to see if creatures you control have total power 8 or greater both as it would trigger and as it resolves
This is especially true because Pokmon Sun and Moon and Pokmon Sword and Shield sets are beginning to phase out in preparation for the release of the Gen 9 games Pokmon Scarlet and Violet
This may sound like a dream scenario, but if you trade with any regularity, you see trades like this all the time
Take a look: Adventure cards can go on their adventure to exile then enter the battlefield when you cast them from exile
To date, Amethyst/Steel remains the best Lorcana starter deck thanks to the fact it actually included most of what you needed to use this combo in it
They are also available in Set, Draft, and Collector Boosters, where both retro artifacts and schematic artifacts can appear in foil and non-foil