The Sideboard The cards in our sideboard are designed to do three things: help improve our matchup against aggressive creature decks (by far our worst matchup), fight three-mana planeswalkers (especially Teferi, Time Raveler but also Narset, Parter of Veils and Oko, Thief of Crowns), and answer graveyard-based decks (which we actually help by filling their graveyard with our mill spells)
Water Omotics
Mewtwo ex is a basic card and can easily be placed in the Active Spot from the first turn, having 150 HP to absorb any early battle attacks
If you prefer to build an indestructible fortress with Darksteel Forge before using Bolass Citadel to fish out one of the many infinite combos (mana, mill, turns, damage, etc.) artifact decks are known for, you can absolutely do that too
Block icon 3 Effect [Main] Look at 5 cards from the top of your deck