Shiny basically just means a different color scheme than how Pokemon typically appear
A simple card that brings a lot of value, Pheromosa can find extended usage in future metas as well, being a core part of the notorious Grass decks
Putting it into the three-color deck is advisable when the fourth and fifth colors of the theme are so undersupported that they need the help
Theres not really a lot more to it the only real note is that if a currently conniving creature is killed, bounced, exiled, or removed from the battlefield in any other way in response to the connive trigger, you still get to draw the card (or cards) and discard a card (or cards), but youll have a tricky time putting the +1/+1 counter on a creature that is no longer there
Getting to use those cards as removal and then cycle them for draw is pretty powerful
Y'shtola and G'raha Tia quickly rose to the top, though I knew I would include all of the Scions that I could fit into the deck