Landfall — Whenever a land enters the battlefield under your control, you may have target player lose 3 life. If you do, put three +1/+1 counters on Ob Nixilis, the Fallen.

Flying, trample Whenever an opponent searches their library, that player sacrifices a creature and loses 10 life. Whenever another creature dies, put a +1/+1 counter on Ob Nixilis, Unshackled.

({T}: Add {B} or {R}.)

({T}: Add {B} or {R}.) As Blood Crypt enters the battlefield, you may pay 2 life. If you don't, it enters the battlefield tapped.

{2}, {T}: Add {B} for each Swamp you control.

{T}: Add one mana of any color in your commander's color identity.

Dragonskull Summit enters the battlefield tapped unless you control a Swamp or a Mountain. {T}: Add {B} or {R}.

{T}: Add {C}. {B/R}, {T}: Add {B}{B}, {B}{R}, or {R}{R}.

Haunted Ridge enters the battlefield tapped unless you control two or more other lands. {T}: Add {B} or {R}.

{T}, Pay 1 life: Add {B} or {R}. {1}{B}{R}, {T}: Mount Doom deals 1 damage to each opponent. {5}{B}{R}, {T}, Sacrifice Mount Doom and a legendary artifact: Choose up to two creatures, then destroy the rest. Activate only as a sorcery.

({T}: Add {R}.)

({T}: Add {B} or {R}.) Smoldering Marsh enters the battlefield tapped unless you control two or more basic lands.

{T}: Add {C}. {T}: Add {B} or {R}. Sulfurous Springs deals 1 damage to you.

({T}: Add {B}.)

{T}: Add {C}. {T}: Add {B} or {R}. Activate only if you control a Swamp.

+2: Each opponent loses 1 life. You gain life equal to the life lost this way. −2: Create a 5/5 black Demon creature token with flying. You lose 2 life. −8: You get an emblem with "{1}{B}, Sacrifice a creature: You gain X life and draw X cards, where X is the sacrificed creature's power." Ob Nixilis of the Black Oath can be your commander.

+1: You draw a card and you lose 1 life. −3: Destroy target creature. −8: Target opponent gets an emblem with "Whenever a player draws a card, you lose 2 life."

Casualty X. The copy isn't legendary and has starting loyalty X. (As you cast this spell, you may sacrifice a creature with power X. When you do, copy this spell. The copy becomes a token.) +1: Each opponent loses 2 life unless they discard a card. If you control a Demon or Devil, you gain 2 life. −2: Create a 1/1 red Devil creature token with "When this creature dies, it deals 1 damage to any target." −7: Target player draws seven cards and loses 7 life.

Equipped creature has haste and shroud. (It can't be the target of spells or abilities.) Equip {0}

{T}: Add one mana of any color in your commander's color identity.

{T}: Add one mana of any color that a land an opponent controls could produce.

{T}, Sacrifice Jeweled Lotus: Add three mana of any one color. Spend this mana only to cast your commander.

{T}: Add {C}. {1}, {T}, Sacrifice Mind Stone: Draw a card.

{1}, {T}: Add {B}{R}.

{T}: Add {C}{C}.

Search your library for a card, put that card into your hand, then shuffle.

Search your library for a card, put that card into your hand, then shuffle.

Search your library for a card, put that card into your hand, then shuffle. You lose 3 life.

Suspend 2—{1}{B} (Rather than cast this card from your hand, pay {1}{B} and exile it with two time counters on it. At the beginning of your upkeep, remove a time counter. When the last is removed, you may cast it without paying its mana cost.) Search your library for a card, put that card into your hand, then shuffle.