These might change the game rules or provide interesting things to do on your turn, like making your opponent miss their attacks or removing damage counters when your opponent isnt looking
Grading a Pokmon card means sending it to a professional third-party service that authenticates the card, evaluates its condition, and assigns a numerical gradeusually from 1 (Poor) to 10 (Gem Mint)
The best two are likely Arc Trail (8) and Lightning Bolt (8.5) for their high efficiency and blowout potential
With other complementary artifact mana sources like Thran Dynamo and Grim Monolith, decks could count on being able to get the kind of mana you'd need to justify packing the cards that would let you use the mana from Metalworker to deliver the knockout blow, and their presence lets you turn that Metalworker mana into permanent giant amounts of mana rather than just a one shot deal
If Polyraptor leaves the battlefield before its triggered ability resolves, most likely because it was dealt lethal damage, the token will still enter the battlefield as a copy of Polyraptor, using Polyraptor's copiable values from when it was last on the battlefield