Mercury is a fairly obscure deck strategy. It involes using δ Starmie and δ Gardevoir to produce and move Metal energies around in a nature similar to that of DragTrode. The δ Gardevoir has Energy Jump; the same power that Skyridge Alakazam had. From what I've seen so far, the actual deck itself has not yet been refined to the point to where it can become an archetype (on contrary to what I thought before). Almost all Mercury decks use Scizor-ex. What does not seem to be consistent is the drawing engine. I've seen it with EX: FrLg Pidgeot, EX: HL Jirachi, and one member here commented that they've seen it with EX: DS Porygon2.
Regardless of what drawing engine is used, the deck uses δ Gardevoir as a primary attacker and Scizor-ex as a secondary attacker. δ Gardevoir is tanked up with 3-4 metals and attacks with Black Magic. Once it has enough damage on it, it starts to hit the bench.
For the most part, it doesn't take much to realize that δ Starmie works similar to that of Dark Electrode. I've speculated that δ Starmie would be used with EX: HL and EX: DX Metagross, as opposed to δ Gardevoir. It makes more sense to me since the EX: DX Metagross can recover Metal Energies.
Not suprisingly, Battle Frontier hurts the deck badly. I am not sure how it matches up against PowDaCham! While Wise Aura would shut down Metal Navigation and Energy Jump, the deck has an elemental advantage against Medicham-ex. I would expect that it matches up well against QueenDom, ZRE, and Ludicargo. It probably breaks even against MetaKnight. It most likely loses against DragTrode, RockLock, LBS, and Slowking decks.
Overall, it is difficult to say what direction it is headed in. I haven't played against it yet. I think it will become more powerful once Worlds comes and goes, since it is relatively unaffected by the format change.
This is what I know so far. Feel free to correct me if you believe there are any misconceptions.
