Xenan Witching Burden (Master)

This is the deck I used to get from diamond 3 to master (27:8). Its a grindy midrange deck built around Grodovs Burden, Eremots Machinations and Witching Hour. The gameplan is relatively flexible and can be adapted based on your opponents deck. The deck has a lot of small synergies that can be used in different ways (e.g. Defile and Temple give you Machinations Tragets; Machinations gives Seedling overwhelm, with Burden you can start overwhelm killer chains; Burden and Witching Hour is completly ridiculous; Tasbu and corrupted shades, Devour, killer units and Nahids Faithful to draw cards; Azindel and overwhelm units from Machinations; sacrificing units with summoning sickness while having Burden to transform them into instant damage; resummoning Nahids Faithful to profit of the 2/2 buff several times etc.).
Against aggressive decks you want early interaction like Defile, Blightmoth and Desert Alchemist. Try to get control of the board before your health drops to low (usually around turn 4-5). Pesky Seedling can really help with that because he can kill smaller 1 or 2 drops and stay on the board for more blocks after that (even providing a shade that can jump-block or be sacrificed for Devour or Nahids Faithful later). The best market options in those matchups are usually Tasbu if you just need a big unit (depends on if your opponent has removal) and Temple, if the board is already stabillised. Azindel and Burden can close out those games, but they are usually worse in the early game. Cards to Market away are usually Witching Hour and Nahids Distillation and sometimes Eremots Machinations.
Against other Midrange decks you can be a bit more relaxed and value Alchemist and Banish over Defile. Merchants and card draw become more important, but you also need to try to keep the board in check. All market cards are potentially good, but it depends a bit on the exact matchup. Tasbu is worse against primal decks because of TTS, and Burden is worse against decks that run relic removal. Azindel and Temple depend on the board state (Azindel is best on a board with free attacks for you, Temple is best on a empty or stabilised board and a bit worse against decks with Jekk or shadow Icaria). Temple is also really impotant against Xenan Reanimator, so try to get it down early and stall from then onwards until you can get Burden and either Witching Hour or Eremots Machinations going. Cards to market away are usually Defile and sometimes Banish, Witching Hour or smaller units.
Against control you try to put some pressure on while not overcommiting (always keep in mind which mass removal they can have (e.g. AAC Feln has Hailstorm on 3, Malediction on 4 if they played Transpose and 6 damage Hailstorm if they have it and Prodigious Sorcery; FJP has Hailstorm and Harsh Rule etc.), and what they likely have (based on specific play patterns you can sometimes deduct if they have Hailstorm or Harsh Rule). Your market and high value cards like Nahids Distillation, Eremots Machinatons and Witching Hour are really important in this matchup. Try to use them to outgrind removal and boardclears. Azindel is also really good if you are able to keep 2 or 3 small units on the board (Smuggler with Ambush is always already 1). Cards to market away are Defile, Banish (sometimes you need it for small relics) and sometiems blightmoth or Seedling.
Good luck and have fun!