This deck uses Blaziken's Firestarter and/or Latias ex δ's Fellow Boost to accelerate Energy for big attacks. Blaziken ex is the main attacker, with its Volcanic Ash being able to snipe anything for 100 damage. Latias can also attack with Power Crush, doing 90 damage for 3 Energy. Included is a Mewtwo δ to help get Energy onto their proper targets, for times when you're using Fellow Boost but not attacking with Latias, or when you need to get Energy onto your Active Pokémon (Firestarter only attaches to the Bench).
Holon Mentor for Jirachi, retreat your starter to it (note that if you started with Latias (ex) δ, you can use Latios ex δ's Link Wing for free retreat), and use Wishing Star to set up. Get a Pidgeot and Blaziken into play, and start using Firestarter to recover Energy from the discard.
Meanwhile, build a Blaziken ex on your Bench. When you go on the offensive, Blaziken ex is usually the first to attack, using Volcanic Ash to snipe engine Pokémon like Pidgeot, destroying your opponent's ability to rebuild. After discarding 2 Energy for Volcanic Ash, it can usually only Blaze Kick afterward, but you can Firestarter Energy onto your Bench and use Mewtwo δ to transfer it to your Active Blaziken ex for another Volcanic Ash, or use Warp Point to get Blaziken ex back to the Bench (sending out a free retreater), attach 2 Energy (one from hand, one from Firestarter), then retreat and Volcanic Ash again.
Latias ex δ is the secondary attacker, and is better if you need to 2HKO the opponent's Active Pokémon. Power Crush only discards if it KOs, so the first hit is free.
This deck has Mewtwo δ to provide an answer to the problem, "how do you get Energy from Firestarter to the Active Pokémon, given that it can only attach to the Bench?" Note that it can only move basic Fire Energy, not δ Rainbow Energy.
Mewtwo δ and Latios ex δ can attack if the situation calls for it, using δ Rainbow Energy for the Metal or Water Energy requirements.
Rayquaza ex, Multi Energy: Replaces Latias ex δ and δ Rainbow Energy. Alternative attacker, can do 120 for 3 Energy (but all get discarded), and resists Water which Blaziken ex is weak to.
More Warp Point, Switch: Replaces Mewtwo δ. After a big attack, you use these to get your depleted attacker to the Bench to Firestarter Energy onto it.
This deck hits really hard. 90 and 100 damage are on the higher end of damage that you can do in one hit.
Blaziken ex's Volcanic Ash 1HKOs Pidgeot, a common support Pokémon in other decks. When you have a Pidgeot and they don't, you are usually favored. Opposing Pidgeot decks are likely also Stage 2-based; they can end up with dead cards rotting in hand like Rare Candy without a Stage 2 or vice versa, situations that Pidgeot would have Quick Searched them out of.
Being able to snipe Stage 1s in Stage 2 decks that forgo the usual Rare Candy (e.g. Bombtar, Dragtrode, some δ decks that use Fearow δ instead of Pidgeot) can also set the opponent back by a lot; you've just taken out 2 of their cards (a Basic and Stage 1), maybe even some Energy on it, with one Volcanic Ash.
This deck can attach up to 3 Energy per turn (1 from Firestarter, 1 from Fellow Boost, and 1 from the per-turn attachment), assuming only 1 Blaziken in play. If your opponent plays too passively and refuses to KO Jirachi and give you an opportunity to get an attacker in safely, you can sit there and accelerate lots of Energy onto your Pokémon until you have two fully loaded attackers ready to spring into action.
This deck is unaffected by Crystal Beach.
Both attackers in this deck are weak to Psychic. Latias δ can buy some time against Psychic-types.
Lunatone and Solrock. While Solrock is well-known for shutting down Pidgeot with Luna Shade, Lunatone gets to join in on the fun against this deck too, with Sol Shade shutting down Blaziken's Firestarter and Mewtwo δ's Delta Switch. Note that Lunatone does not turn off Latias ex δ's Fellow Boost, so you can still use that to accelerate. Lunatone and Solrock are often used in ex decks, so Latios ex δ can stall against them with Ice Barrier.
Jirachi ex prevents you from using Powers with Shield Beam. You can set up with Latias δ's Spearhead instead, get lucky with Torchic's Hypnotic Gaze or Combusken's Smokescreen to buy a turn of Power usage, or build Latios ex δ to force it away.
Dugtrio and Cloyster δ prevent you from damaging the Bench. Latias δ turns off their Bodies.
Cursed Stone and Desert Ruins can pile lots of damage onto your Pokémon.