X Marks the spot was the chosen name because of all the spells with X in the cost. These cards are good mana sinks for the infinity of mana that this deck produces.
The main combo for getting infinite mana (it can be pulled off at turn 4):
Kiora's Follower or Voyaging Satyr + Land, for example Nykthos, Shrine to Nyx(Optional) and one or a few Verdant Haven or Market Festival. Tap land for more than 5 mana, untap with untapper. untap your land untapper with Thassa's Ire, rinse and repeat for infinite mana. Proceed to pump all this mana in a mana sink like Villainous Wealth or Genesis Hydra to get another win-con like Hydra Broodmaster
The goal of the rest of the cards is to stabilize early game to not die to aggro, or to gather other combo pieces.
The combo is not the only way to win, but once you hit it and have a card in hand that can make use of it, you are pretty sure to win. It's actually pretty competitive even if you do not pull off the combo. The land enchantments work really well in out-pacing the opponent and this deck actually fares best against mid range decks like abzan midrange or sultai whip.
Bad matchups are anything that's very aggresive like red deck wins, boros aggro, heroic type aggro decks etc. These are considered bad matchups, but are definately not dead games. Seeing as the largest part of the meta is midrange, this deck does quite well.
I´m not sure about the sideboard yet so i could use some suggestions on that
