This card is the main card of the deck. At a glance, 120 HP is pretty good, almost guaranteeing that Palkia G Lv. X will be around for at least one turn. Lost Cyclone looks like it can be disruptive to your opponent, and is used to your benefit (which is explained below.) Hydro Shot is a great attack. You can start using it in four turns or even three (with an Energy Gain or a Double Colorless Energy). A Retreat Cost of two is heavy, but not unbearable. Truly, the only bad thing about this card is its Lightning Weakness. Having Lightning Weakness means Luxray GL Lv. X will use Flash Impact to KO Palkia G Lv. X in one shot. Since Luxray GL Lv. X is probably the most popular card in the format, this could lead to problems.
Let’s look at Lost Cyclone again. You get to send Pokemon on your bench to the Lost Zone until you have three Benched Pokemon, and your opponent does the same. This can be good or bad for your opponent; they can remove benched support Pokemon like Uxie or Azelf, or they can remove a damaged attacker from the game so you can’t get a cheap prize. Lost Cyclone is very important to this deck because you run Mesprits. Lost Cyclone can clear the Mesprits off your bench so you can drop more, Psychic Binding your opponent four times in a row. This can slow your opponent down a lot.
Hydro Shot is Palkia G Lv. X’s only attack. It’s a bit more expensive than Garchomp C’s Dragon Rush, but unlike Dragon Rush, you can use it turn after turn. Having a cost of (W)(W)(C)(C) is a lot more convenient than a cost of (W)(W)(W)(C), because you can fulfill the two Colorless Requirements with Double Colorless Energy. So, on your first turn, you attach a Water Energy. On your second turn, attach another Water Energy. On your third turn, attach a Double Colorless Energy and Hydro Shot. Next turn, attach another Double Colorless Energy and Hydro Shot. You can keep doing this as long as you have Double Colorless Energies in your hand. Otherwise, you can simply drop another Energy and an Energy Gain onto Palkia G Lv. X to continue Hydro Shotting. The 80 damage that Hydro Shot does is just enough to pick off a Claydol that your opponent would use to set up, and Hydro Shot can also KO a Luxray GL or Garchomp that is threatening you.