pokemon card arceus gx [sm12] & Dialga & Palkia 065/095〈RR〉 have for your premier collection. Arceus & Dialga & Palkia-GX

While your LGS might not grade them, they can help you figure out if anything in your collection is worth trading (assuming you take the time to find the most likely cards

The token created by the second ability will be a copy of whatever card is exiled with Mimic Vat at the time the ability resolves

But with flash you can also just drop your hand EOT and then untap and swing with your newly minted stuff or keep it from a round of targeted removal or after someone casts a mass removal spell

You can bank your mana, you can use token-doublers

Sure, the ceiling on a creature like Legion Warboss is pretty high if it isnt answered, but theres not really a lot of work you have to do to make that happen, really