msem-instigator

Barren Boneyard enters tapped.
{T}: Add {B}.
{2/B}{2/B}: Barren Boneyard becomes a 2/3 black Elemental creature with deathtouch until end of turn. It's still a land.

As Barren Desolation enters, you may pay 2 life. If you don't, Barren Desolation enters tapped.
{T}, Sacrifice Barren Desolation: Search your library for a Plains or Swamp card, put it onto the battlefield, then shuffle.

Barren Vista enters tapped.
{T}: Add {U} or {B}.
{1}, {T}: Add one mana of any color.

Basin Fortress enters tapped unless you control a basic land.
{T}: Add {B} or {G}.

{T}: Add {C}.
{T}: Add one mana of any color. Spend this mana only to cast enchantment spells or to activate an ability of an enchantment.
When Bastion, Node of the Free is destroyed, return it to its owner's hand.

At the beginning of your upkeep, Bauble of Infinites deals 2 damage to each opponent and you gain 2 life.

(Transform this if it's not attached to a creature. Pay {1}{U} as a sorcery to unattach it.)
Enchant creature you control
Bay-Bandit's Snapper's rider gets +1/+2.
Whenever Bay-Bandit's Snapper's rider deals combat damage to a player, you draw two cards.

Whenever you cast an instant or sorcery spell, each opponent loses 1 life and Beast of Pestilence gets +1/+1 until end of turn.

(Transform this if it's not attached to a creature. Pay {2}{B}{B} as a sorcery to unattach it.)
Enchant creature you control
Belmord Blood-Coach's rider gets +3/+3 and has deathtouch.
Whenever Belmord Blood-Coach's rider attacks, you may return target creature card with mana value less than its rider's power from your graveyard to the battlefield tapped.

Enchant creature
At the beginning of the upkeep of enchanted creature's controller, Betrayer's Mantle deals 3 damage to that player.

Bigroot Valley enters tapped.
{T}: Add {R} or {G}.
{1}, {T}: Add one mana of any color.

When Bio-Sequencer enters, conjure a card named Data-Point into your hand. (It's a sorcery that costs {2} with “Draw a card.”)
{1}, {T}, Sacrifice Bio-Sequencer: Add one mana of any color.

When Blackwall's Edge enters, if you control four or more lands, you may have each player conjure a card named Data-Point into their hand. (It's a sorcery that costs {2} with “Draw a card.”)
{T}: Add {C}.
When Blackwall's Edge is destroyed, return it to its owner's hand.

At the beginning of your upkeep, if Blade of Ancestors isn't attached to a creature, create a 1/1 white Soldier creature token, then attach Blade of Ancestors to it.
Equipped creature gets +1/+1.
Equip {2}

({T}: Add {U}, {B}, or {R}.)
Bleak Dominion enters tapped.

Bleak Shoreline enters tapped unless you control an Island.
{T}: Add {W} or {B}.

Bleakrealm Moor enters tapped unless you played it from exile.
{T}: Add {B} or {R}.

Blessed Grounds enters tapped. When it enters, surveil 1. (Look at the top card of your library. You may put it into your graveyard.)
{T}: Add {G} or {W}.

Enchant land
Whenever enchanted land is tapped for mana, its controller adds two mana in any combination of colors (in addition to the mana the land produces.)

({T}: Add {W} or {B}.)
As Blessed Mausoleum enters, you may pay {1}. If you don't, Blessed Mausoleum enters tapped.

{T}: Add {C}.
Dominance — {1}, {T}: Blistering Boneyard deals 1 damage to each opponent. Activate only if you control the creature with the greatest power or tied for the greatest power.

Flying, menace
Sacrifice a creature: Put two +1/+1 counters on Bloodclaw Demon. It gains indestructible until end of turn.

Bloodfell Caves enters tapped.
When Bloodfell Caves enters, you gain 1 life.
{T}: Add {B} or {R}.

({T}: Add {R}.)
Bloodriver enters tapped.
When Bloodriver enters, target creature you control gains haste until end of turn.