For the cost of two mana plus a sacrificed creature, this instant is game-changing if used at the right time to counter a big board wipe, and given the creature/enchantment focus of this deck, this is invaluable.
Try the Premium Pass free trial Though it is quite well hidden, there is actually a two week free trial for Pokemon TCG Pockets Premium Pass for new users, and I recommend making the most of that
Dark Ritual allows black so many sick turn one plays, it isn't funny
A bounce land that turns bodies into ramp, the perfect option for Monowhite
The shards lands, before being reprinted in the Commander decks, used to go for $2-$3 at their highest point
You still need to abide by Commander rules, but to prevent limitations in deck builds, there are some workarounds implemented