KETHIS, HIDDEN HAND Running all of your favorites in one deck can be challenging, especially as legendary-matters is so broad
Like most Pokmon cards, the value of Porygon 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 (Paradox Rift)
[M][M][C][C] Sword Star (VSTAR Power): 310 damage
Low curve decks and token based decks are probably the only decks that would want him, as getting 2 permanents to enter the table on your term consistantly isn't free, unless you do bouncy things or generate tokens constantly
It is sufficiently over powered that it is one of a few cards I no longer bother to run in my cube
It's also convenient for providing targets for "Vampire Scourge's" revival effect