Like most Magic: The Gathering cards, the value of Mechtitan Core depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (Kamigawa: Neon Dynasty)
Decks I would recommend Penny to be played in: any deck that plays Basic Pokemon Thorton For similar reasons as Penny, Thorton can act as answers to lock situations, like Mawile, by switching your Active Pokemon with a Pokemon in your Discard Pile
The Amber cards, while there are some strong glimmers, are more focused on giving buffs and enhancements to other cards, adding to the stats of player cards, or removing stats from opponent cards
Showcase: Bloomburrow These are neat, and Ive learned not to overlook the power of cute when it comes to Magic cards
They thought they could beat you
Key things to check on the card : the illustration, text, border color and size, set symbol, set number, HP value, attack values, energy symbols, and weaknesses/resistances